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<h1 id="62">6.2 哈希冲突<a class="headerlink" href="#62" title="Permanent link">¶</a></h1>
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<p>上节提到，<strong>通常情况下哈希函数的输入空间远大于输出空间</strong>，因此理论上哈希冲突是不可避免的。比如，输入空间为全体整数，输出空间为数组容量大小，则必然有多个整数映射至同一数组索引。</p>
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<p>哈希冲突会导致查询结果错误，严重影响哈希表的可用性。为解决该问题，我们可以每当遇到哈希冲突时就进行哈希表扩容，直至冲突消失为止。此方法简单粗暴且有效，但效率太低，因为哈希表扩容需要进行大量的数据搬运与哈希值计算。为了提升效率，我们可以采用以下思路。</p>
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<p>哈希冲突会导致查询结果错误，严重影响哈希表的可用性。为解决该问题，我们可以每当遇到哈希冲突时就进行哈希表扩容，直至冲突消失为止。此方法简单粗暴且有效，但效率太低，因为哈希表扩容需要进行大量的数据搬运与哈希值计算。为了提升效率，我们可以采用以下策略。</p>
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<ol>
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<li>改良哈希表数据结构，<strong>使得哈希表可以在存在哈希冲突时正常工作</strong>。</li>
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<li>仅在必要时，即当哈希冲突比较严重时，才执行扩容操作。</li>
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@@ -3654,94 +3654,104 @@
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<a id="__codelineno-1-13" name="__codelineno-1-13" href="#__codelineno-1-13"></a><span class="w"> </span><span class="n">buckets</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="n">capacity</span><span class="p">);</span>
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<a id="__codelineno-1-14" name="__codelineno-1-14" href="#__codelineno-1-14"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-15" name="__codelineno-1-15" href="#__codelineno-1-15"></a>
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<a id="__codelineno-1-16" name="__codelineno-1-16" href="#__codelineno-1-16"></a><span class="w"> </span><span class="cm">/* 哈希函数 */</span>
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<a id="__codelineno-1-17" name="__codelineno-1-17" href="#__codelineno-1-17"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-18" name="__codelineno-1-18" href="#__codelineno-1-18"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span>
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<a id="__codelineno-1-19" name="__codelineno-1-19" href="#__codelineno-1-19"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-20" name="__codelineno-1-20" href="#__codelineno-1-20"></a>
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<a id="__codelineno-1-21" name="__codelineno-1-21" href="#__codelineno-1-21"></a><span class="w"> </span><span class="cm">/* 负载因子 */</span>
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<a id="__codelineno-1-22" name="__codelineno-1-22" href="#__codelineno-1-22"></a><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-23" name="__codelineno-1-23" href="#__codelineno-1-23"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="n">size</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="n">capacity</span><span class="p">;</span>
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<a id="__codelineno-1-16" name="__codelineno-1-16" href="#__codelineno-1-16"></a><span class="w"> </span><span class="cm">/* 析构方法 */</span>
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<a id="__codelineno-1-17" name="__codelineno-1-17" href="#__codelineno-1-17"></a><span class="w"> </span><span class="o">~</span><span class="n">HashMapChaining</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-18" name="__codelineno-1-18" href="#__codelineno-1-18"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-19" name="__codelineno-1-19" href="#__codelineno-1-19"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucket</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-20" name="__codelineno-1-20" href="#__codelineno-1-20"></a><span class="w"> </span><span class="c1">// 释放内存</span>
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<a id="__codelineno-1-21" name="__codelineno-1-21" href="#__codelineno-1-21"></a><span class="w"> </span><span class="k">delete</span><span class="w"> </span><span class="n">pair</span><span class="p">;</span>
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<a id="__codelineno-1-22" name="__codelineno-1-22" href="#__codelineno-1-22"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-23" name="__codelineno-1-23" href="#__codelineno-1-23"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-24" name="__codelineno-1-24" href="#__codelineno-1-24"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-25" name="__codelineno-1-25" href="#__codelineno-1-25"></a>
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<a id="__codelineno-1-26" name="__codelineno-1-26" href="#__codelineno-1-26"></a><span class="w"> </span><span class="cm">/* 查询操作 */</span>
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<a id="__codelineno-1-27" name="__codelineno-1-27" href="#__codelineno-1-27"></a><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">get</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-28" name="__codelineno-1-28" href="#__codelineno-1-28"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
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<a id="__codelineno-1-29" name="__codelineno-1-29" href="#__codelineno-1-29"></a><span class="w"> </span><span class="c1">// 遍历桶，若找到 key 则返回对应 val</span>
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<a id="__codelineno-1-30" name="__codelineno-1-30" href="#__codelineno-1-30"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">])</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-31" name="__codelineno-1-31" href="#__codelineno-1-31"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-32" name="__codelineno-1-32" href="#__codelineno-1-32"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="p">;</span>
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<a id="__codelineno-1-33" name="__codelineno-1-33" href="#__codelineno-1-33"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-34" name="__codelineno-1-34" href="#__codelineno-1-34"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-35" name="__codelineno-1-35" href="#__codelineno-1-35"></a><span class="w"> </span><span class="c1">// 若未找到 key 则返回 nullptr</span>
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<a id="__codelineno-1-36" name="__codelineno-1-36" href="#__codelineno-1-36"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">nullptr</span><span class="p">;</span>
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<a id="__codelineno-1-37" name="__codelineno-1-37" href="#__codelineno-1-37"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-38" name="__codelineno-1-38" href="#__codelineno-1-38"></a>
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<a id="__codelineno-1-39" name="__codelineno-1-39" href="#__codelineno-1-39"></a><span class="w"> </span><span class="cm">/* 添加操作 */</span>
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<a id="__codelineno-1-40" name="__codelineno-1-40" href="#__codelineno-1-40"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">put</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-41" name="__codelineno-1-41" href="#__codelineno-1-41"></a><span class="w"> </span><span class="c1">// 当负载因子超过阈值时，执行扩容</span>
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<a id="__codelineno-1-42" name="__codelineno-1-42" href="#__codelineno-1-42"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loadFactor</span><span class="p">()</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="n">loadThres</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-43" name="__codelineno-1-43" href="#__codelineno-1-43"></a><span class="w"> </span><span class="n">extend</span><span class="p">();</span>
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<a id="__codelineno-1-26" name="__codelineno-1-26" href="#__codelineno-1-26"></a><span class="w"> </span><span class="cm">/* 哈希函数 */</span>
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<a id="__codelineno-1-27" name="__codelineno-1-27" href="#__codelineno-1-27"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-28" name="__codelineno-1-28" href="#__codelineno-1-28"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">key</span><span class="w"> </span><span class="o">%</span><span class="w"> </span><span class="n">capacity</span><span class="p">;</span>
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<a id="__codelineno-1-29" name="__codelineno-1-29" href="#__codelineno-1-29"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-30" name="__codelineno-1-30" href="#__codelineno-1-30"></a>
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||||
<a id="__codelineno-1-31" name="__codelineno-1-31" href="#__codelineno-1-31"></a><span class="w"> </span><span class="cm">/* 负载因子 */</span>
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<a id="__codelineno-1-32" name="__codelineno-1-32" href="#__codelineno-1-32"></a><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">loadFactor</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-33" name="__codelineno-1-33" href="#__codelineno-1-33"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="n">size</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="p">(</span><span class="kt">double</span><span class="p">)</span><span class="n">capacity</span><span class="p">;</span>
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<a id="__codelineno-1-34" name="__codelineno-1-34" href="#__codelineno-1-34"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-35" name="__codelineno-1-35" href="#__codelineno-1-35"></a>
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<a id="__codelineno-1-36" name="__codelineno-1-36" href="#__codelineno-1-36"></a><span class="w"> </span><span class="cm">/* 查询操作 */</span>
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<a id="__codelineno-1-37" name="__codelineno-1-37" href="#__codelineno-1-37"></a><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">get</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-38" name="__codelineno-1-38" href="#__codelineno-1-38"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
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<a id="__codelineno-1-39" name="__codelineno-1-39" href="#__codelineno-1-39"></a><span class="w"> </span><span class="c1">// 遍历桶，若找到 key 则返回对应 val</span>
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<a id="__codelineno-1-40" name="__codelineno-1-40" href="#__codelineno-1-40"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">])</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-41" name="__codelineno-1-41" href="#__codelineno-1-41"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-42" name="__codelineno-1-42" href="#__codelineno-1-42"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="p">;</span>
|
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<a id="__codelineno-1-43" name="__codelineno-1-43" href="#__codelineno-1-43"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-44" name="__codelineno-1-44" href="#__codelineno-1-44"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-45" name="__codelineno-1-45" href="#__codelineno-1-45"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
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<a id="__codelineno-1-46" name="__codelineno-1-46" href="#__codelineno-1-46"></a><span class="w"> </span><span class="c1">// 遍历桶，若遇到指定 key ，则更新对应 val 并返回</span>
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<a id="__codelineno-1-47" name="__codelineno-1-47" href="#__codelineno-1-47"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">])</span><span class="w"> </span><span class="p">{</span>
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<a id="__codelineno-1-48" name="__codelineno-1-48" href="#__codelineno-1-48"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
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<a id="__codelineno-1-49" name="__codelineno-1-49" href="#__codelineno-1-49"></a><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">;</span>
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||||
<a id="__codelineno-1-50" name="__codelineno-1-50" href="#__codelineno-1-50"></a><span class="w"> </span><span class="k">return</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-51" name="__codelineno-1-51" href="#__codelineno-1-51"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-52" name="__codelineno-1-52" href="#__codelineno-1-52"></a><span class="w"> </span><span class="p">}</span>
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<a id="__codelineno-1-53" name="__codelineno-1-53" href="#__codelineno-1-53"></a><span class="w"> </span><span class="c1">// 若无该 key ，则将键值对添加至尾部</span>
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<a id="__codelineno-1-54" name="__codelineno-1-54" href="#__codelineno-1-54"></a><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">].</span><span class="n">push_back</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Pair</span><span class="p">(</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="p">));</span>
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<a id="__codelineno-1-55" name="__codelineno-1-55" href="#__codelineno-1-55"></a><span class="w"> </span><span class="n">size</span><span class="o">++</span><span class="p">;</span>
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<a id="__codelineno-1-56" name="__codelineno-1-56" href="#__codelineno-1-56"></a><span class="w"> </span><span class="p">}</span>
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||||
<a id="__codelineno-1-57" name="__codelineno-1-57" href="#__codelineno-1-57"></a>
|
||||
<a id="__codelineno-1-58" name="__codelineno-1-58" href="#__codelineno-1-58"></a><span class="w"> </span><span class="cm">/* 删除操作 */</span>
|
||||
<a id="__codelineno-1-59" name="__codelineno-1-59" href="#__codelineno-1-59"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-60" name="__codelineno-1-60" href="#__codelineno-1-60"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-61" name="__codelineno-1-61" href="#__codelineno-1-61"></a><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">];</span>
|
||||
<a id="__codelineno-1-62" name="__codelineno-1-62" href="#__codelineno-1-62"></a><span class="w"> </span><span class="c1">// 遍历桶，从中删除键值对</span>
|
||||
<a id="__codelineno-1-63" name="__codelineno-1-63" href="#__codelineno-1-63"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">bucket</span><span class="p">.</span><span class="n">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-64" name="__codelineno-1-64" href="#__codelineno-1-64"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bucket</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-65" name="__codelineno-1-65" href="#__codelineno-1-65"></a><span class="w"> </span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bucket</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
|
||||
<a id="__codelineno-1-66" name="__codelineno-1-66" href="#__codelineno-1-66"></a><span class="w"> </span><span class="n">bucket</span><span class="p">.</span><span class="n">erase</span><span class="p">(</span><span class="n">bucket</span><span class="p">.</span><span class="n">begin</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w"> </span><span class="c1">// 从中删除键值对</span>
|
||||
<a id="__codelineno-1-67" name="__codelineno-1-67" href="#__codelineno-1-67"></a><span class="w"> </span><span class="k">delete</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w"> </span><span class="c1">// 释放内存</span>
|
||||
<a id="__codelineno-1-68" name="__codelineno-1-68" href="#__codelineno-1-68"></a><span class="w"> </span><span class="n">size</span><span class="o">--</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-69" name="__codelineno-1-69" href="#__codelineno-1-69"></a><span class="w"> </span><span class="k">return</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-70" name="__codelineno-1-70" href="#__codelineno-1-70"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-71" name="__codelineno-1-71" href="#__codelineno-1-71"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-72" name="__codelineno-1-72" href="#__codelineno-1-72"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-73" name="__codelineno-1-73" href="#__codelineno-1-73"></a>
|
||||
<a id="__codelineno-1-74" name="__codelineno-1-74" href="#__codelineno-1-74"></a><span class="w"> </span><span class="cm">/* 扩容哈希表 */</span>
|
||||
<a id="__codelineno-1-75" name="__codelineno-1-75" href="#__codelineno-1-75"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">extend</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-76" name="__codelineno-1-76" href="#__codelineno-1-76"></a><span class="w"> </span><span class="c1">// 暂存原哈希表</span>
|
||||
<a id="__codelineno-1-77" name="__codelineno-1-77" href="#__codelineno-1-77"></a><span class="w"> </span><span class="n">vector</span><span class="o"><</span><span class="n">vector</span><span class="o"><</span><span class="n">Pair</span><span class="w"> </span><span class="o">*>></span><span class="w"> </span><span class="n">bucketsTmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-78" name="__codelineno-1-78" href="#__codelineno-1-78"></a><span class="w"> </span><span class="c1">// 初始化扩容后的新哈希表</span>
|
||||
<a id="__codelineno-1-79" name="__codelineno-1-79" href="#__codelineno-1-79"></a><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">*=</span><span class="w"> </span><span class="n">extendRatio</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-80" name="__codelineno-1-80" href="#__codelineno-1-80"></a><span class="w"> </span><span class="n">buckets</span><span class="p">.</span><span class="n">clear</span><span class="p">();</span>
|
||||
<a id="__codelineno-1-81" name="__codelineno-1-81" href="#__codelineno-1-81"></a><span class="w"> </span><span class="n">buckets</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="n">capacity</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-82" name="__codelineno-1-82" href="#__codelineno-1-82"></a><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-83" name="__codelineno-1-83" href="#__codelineno-1-83"></a><span class="w"> </span><span class="c1">// 将键值对从原哈希表搬运至新哈希表</span>
|
||||
<a id="__codelineno-1-84" name="__codelineno-1-84" href="#__codelineno-1-84"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucketsTmp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-85" name="__codelineno-1-85" href="#__codelineno-1-85"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucket</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-86" name="__codelineno-1-86" href="#__codelineno-1-86"></a><span class="w"> </span><span class="n">put</span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-87" name="__codelineno-1-87" href="#__codelineno-1-87"></a><span class="w"> </span><span class="c1">// 释放内存</span>
|
||||
<a id="__codelineno-1-88" name="__codelineno-1-88" href="#__codelineno-1-88"></a><span class="w"> </span><span class="k">delete</span><span class="w"> </span><span class="n">pair</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-89" name="__codelineno-1-89" href="#__codelineno-1-89"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-90" name="__codelineno-1-90" href="#__codelineno-1-90"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-91" name="__codelineno-1-91" href="#__codelineno-1-91"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-92" name="__codelineno-1-92" href="#__codelineno-1-92"></a>
|
||||
<a id="__codelineno-1-93" name="__codelineno-1-93" href="#__codelineno-1-93"></a><span class="w"> </span><span class="cm">/* 打印哈希表 */</span>
|
||||
<a id="__codelineno-1-94" name="__codelineno-1-94" href="#__codelineno-1-94"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-95" name="__codelineno-1-95" href="#__codelineno-1-95"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-96" name="__codelineno-1-96" href="#__codelineno-1-96"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"["</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-97" name="__codelineno-1-97" href="#__codelineno-1-97"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucket</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-98" name="__codelineno-1-98" href="#__codelineno-1-98"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" -> "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">", "</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-45" name="__codelineno-1-45" href="#__codelineno-1-45"></a><span class="w"> </span><span class="c1">// 若未找到 key 则返回 nullptr</span>
|
||||
<a id="__codelineno-1-46" name="__codelineno-1-46" href="#__codelineno-1-46"></a><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="k">nullptr</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-47" name="__codelineno-1-47" href="#__codelineno-1-47"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-48" name="__codelineno-1-48" href="#__codelineno-1-48"></a>
|
||||
<a id="__codelineno-1-49" name="__codelineno-1-49" href="#__codelineno-1-49"></a><span class="w"> </span><span class="cm">/* 添加操作 */</span>
|
||||
<a id="__codelineno-1-50" name="__codelineno-1-50" href="#__codelineno-1-50"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">put</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="n">val</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-51" name="__codelineno-1-51" href="#__codelineno-1-51"></a><span class="w"> </span><span class="c1">// 当负载因子超过阈值时，执行扩容</span>
|
||||
<a id="__codelineno-1-52" name="__codelineno-1-52" href="#__codelineno-1-52"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">loadFactor</span><span class="p">()</span><span class="w"> </span><span class="o">></span><span class="w"> </span><span class="n">loadThres</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-53" name="__codelineno-1-53" href="#__codelineno-1-53"></a><span class="w"> </span><span class="n">extend</span><span class="p">();</span>
|
||||
<a id="__codelineno-1-54" name="__codelineno-1-54" href="#__codelineno-1-54"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-55" name="__codelineno-1-55" href="#__codelineno-1-55"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-56" name="__codelineno-1-56" href="#__codelineno-1-56"></a><span class="w"> </span><span class="c1">// 遍历桶，若遇到指定 key ，则更新对应 val 并返回</span>
|
||||
<a id="__codelineno-1-57" name="__codelineno-1-57" href="#__codelineno-1-57"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">])</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-58" name="__codelineno-1-58" href="#__codelineno-1-58"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-59" name="__codelineno-1-59" href="#__codelineno-1-59"></a><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">val</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-60" name="__codelineno-1-60" href="#__codelineno-1-60"></a><span class="w"> </span><span class="k">return</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-61" name="__codelineno-1-61" href="#__codelineno-1-61"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-62" name="__codelineno-1-62" href="#__codelineno-1-62"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-63" name="__codelineno-1-63" href="#__codelineno-1-63"></a><span class="w"> </span><span class="c1">// 若无该 key ，则将键值对添加至尾部</span>
|
||||
<a id="__codelineno-1-64" name="__codelineno-1-64" href="#__codelineno-1-64"></a><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">].</span><span class="n">push_back</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">Pair</span><span class="p">(</span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">val</span><span class="p">));</span>
|
||||
<a id="__codelineno-1-65" name="__codelineno-1-65" href="#__codelineno-1-65"></a><span class="w"> </span><span class="n">size</span><span class="o">++</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-66" name="__codelineno-1-66" href="#__codelineno-1-66"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-67" name="__codelineno-1-67" href="#__codelineno-1-67"></a>
|
||||
<a id="__codelineno-1-68" name="__codelineno-1-68" href="#__codelineno-1-68"></a><span class="w"> </span><span class="cm">/* 删除操作 */</span>
|
||||
<a id="__codelineno-1-69" name="__codelineno-1-69" href="#__codelineno-1-69"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">remove</span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-70" name="__codelineno-1-70" href="#__codelineno-1-70"></a><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">hashFunc</span><span class="p">(</span><span class="n">key</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-71" name="__codelineno-1-71" href="#__codelineno-1-71"></a><span class="w"> </span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">];</span>
|
||||
<a id="__codelineno-1-72" name="__codelineno-1-72" href="#__codelineno-1-72"></a><span class="w"> </span><span class="c1">// 遍历桶，从中删除键值对</span>
|
||||
<a id="__codelineno-1-73" name="__codelineno-1-73" href="#__codelineno-1-73"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">bucket</span><span class="p">.</span><span class="n">size</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-74" name="__codelineno-1-74" href="#__codelineno-1-74"></a><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">bucket</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">key</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-75" name="__codelineno-1-75" href="#__codelineno-1-75"></a><span class="w"> </span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bucket</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
|
||||
<a id="__codelineno-1-76" name="__codelineno-1-76" href="#__codelineno-1-76"></a><span class="w"> </span><span class="n">bucket</span><span class="p">.</span><span class="n">erase</span><span class="p">(</span><span class="n">bucket</span><span class="p">.</span><span class="n">begin</span><span class="p">()</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w"> </span><span class="c1">// 从中删除键值对</span>
|
||||
<a id="__codelineno-1-77" name="__codelineno-1-77" href="#__codelineno-1-77"></a><span class="w"> </span><span class="k">delete</span><span class="w"> </span><span class="n">tmp</span><span class="p">;</span><span class="w"> </span><span class="c1">// 释放内存</span>
|
||||
<a id="__codelineno-1-78" name="__codelineno-1-78" href="#__codelineno-1-78"></a><span class="w"> </span><span class="n">size</span><span class="o">--</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-79" name="__codelineno-1-79" href="#__codelineno-1-79"></a><span class="w"> </span><span class="k">return</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-80" name="__codelineno-1-80" href="#__codelineno-1-80"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-81" name="__codelineno-1-81" href="#__codelineno-1-81"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-82" name="__codelineno-1-82" href="#__codelineno-1-82"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-83" name="__codelineno-1-83" href="#__codelineno-1-83"></a>
|
||||
<a id="__codelineno-1-84" name="__codelineno-1-84" href="#__codelineno-1-84"></a><span class="w"> </span><span class="cm">/* 扩容哈希表 */</span>
|
||||
<a id="__codelineno-1-85" name="__codelineno-1-85" href="#__codelineno-1-85"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">extend</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-86" name="__codelineno-1-86" href="#__codelineno-1-86"></a><span class="w"> </span><span class="c1">// 暂存原哈希表</span>
|
||||
<a id="__codelineno-1-87" name="__codelineno-1-87" href="#__codelineno-1-87"></a><span class="w"> </span><span class="n">vector</span><span class="o"><</span><span class="n">vector</span><span class="o"><</span><span class="n">Pair</span><span class="w"> </span><span class="o">*>></span><span class="w"> </span><span class="n">bucketsTmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buckets</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-88" name="__codelineno-1-88" href="#__codelineno-1-88"></a><span class="w"> </span><span class="c1">// 初始化扩容后的新哈希表</span>
|
||||
<a id="__codelineno-1-89" name="__codelineno-1-89" href="#__codelineno-1-89"></a><span class="w"> </span><span class="n">capacity</span><span class="w"> </span><span class="o">*=</span><span class="w"> </span><span class="n">extendRatio</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-90" name="__codelineno-1-90" href="#__codelineno-1-90"></a><span class="w"> </span><span class="n">buckets</span><span class="p">.</span><span class="n">clear</span><span class="p">();</span>
|
||||
<a id="__codelineno-1-91" name="__codelineno-1-91" href="#__codelineno-1-91"></a><span class="w"> </span><span class="n">buckets</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="n">capacity</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-92" name="__codelineno-1-92" href="#__codelineno-1-92"></a><span class="w"> </span><span class="n">size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-93" name="__codelineno-1-93" href="#__codelineno-1-93"></a><span class="w"> </span><span class="c1">// 将键值对从原哈希表搬运至新哈希表</span>
|
||||
<a id="__codelineno-1-94" name="__codelineno-1-94" href="#__codelineno-1-94"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucketsTmp</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-95" name="__codelineno-1-95" href="#__codelineno-1-95"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucket</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-96" name="__codelineno-1-96" href="#__codelineno-1-96"></a><span class="w"> </span><span class="n">put</span><span class="p">(</span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="p">,</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="p">);</span>
|
||||
<a id="__codelineno-1-97" name="__codelineno-1-97" href="#__codelineno-1-97"></a><span class="w"> </span><span class="c1">// 释放内存</span>
|
||||
<a id="__codelineno-1-98" name="__codelineno-1-98" href="#__codelineno-1-98"></a><span class="w"> </span><span class="k">delete</span><span class="w"> </span><span class="n">pair</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-99" name="__codelineno-1-99" href="#__codelineno-1-99"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-100" name="__codelineno-1-100" href="#__codelineno-1-100"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"]</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-101" name="__codelineno-1-101" href="#__codelineno-1-101"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-102" name="__codelineno-1-102" href="#__codelineno-1-102"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-103" name="__codelineno-1-103" href="#__codelineno-1-103"></a><span class="p">};</span>
|
||||
<a id="__codelineno-1-100" name="__codelineno-1-100" href="#__codelineno-1-100"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-101" name="__codelineno-1-101" href="#__codelineno-1-101"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-102" name="__codelineno-1-102" href="#__codelineno-1-102"></a>
|
||||
<a id="__codelineno-1-103" name="__codelineno-1-103" href="#__codelineno-1-103"></a><span class="w"> </span><span class="cm">/* 打印哈希表 */</span>
|
||||
<a id="__codelineno-1-104" name="__codelineno-1-104" href="#__codelineno-1-104"></a><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">print</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-105" name="__codelineno-1-105" href="#__codelineno-1-105"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&</span><span class="n">bucket</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">buckets</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-106" name="__codelineno-1-106" href="#__codelineno-1-106"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"["</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-107" name="__codelineno-1-107" href="#__codelineno-1-107"></a><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">Pair</span><span class="w"> </span><span class="o">*</span><span class="n">pair</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">bucket</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
|
||||
<a id="__codelineno-1-108" name="__codelineno-1-108" href="#__codelineno-1-108"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">key</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" -> "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">pair</span><span class="o">-></span><span class="n">val</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">", "</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-109" name="__codelineno-1-109" href="#__codelineno-1-109"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-110" name="__codelineno-1-110" href="#__codelineno-1-110"></a><span class="w"> </span><span class="n">cout</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"]</span><span class="se">\n</span><span class="s">"</span><span class="p">;</span>
|
||||
<a id="__codelineno-1-111" name="__codelineno-1-111" href="#__codelineno-1-111"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-112" name="__codelineno-1-112" href="#__codelineno-1-112"></a><span class="w"> </span><span class="p">}</span>
|
||||
<a id="__codelineno-1-113" name="__codelineno-1-113" href="#__codelineno-1-113"></a><span class="p">};</span>
|
||||
</code></pre></div>
|
||||
</div>
|
||||
<div class="tabbed-block">
|
||||
@@ -4615,10 +4625,7 @@
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
<div class="admonition tip">
|
||||
<p class="admonition-title">Tip</p>
|
||||
<p>当链表很长时，查询效率 <span class="arithmatex">\(O(n)\)</span> 很差，<strong>此时可以将链表转换为“AVL 树”或“红黑树”</strong>，从而将查询操作的时间复杂度优化至 <span class="arithmatex">\(O(\log n)\)</span> 。</p>
|
||||
</div>
|
||||
<p>值得注意的是，当链表很长时，查询效率 <span class="arithmatex">\(O(n)\)</span> 很差。<strong>此时可以将链表转换为“AVL 树”或“红黑树”</strong>，从而将查询操作的时间复杂度优化至 <span class="arithmatex">\(O(\log n)\)</span> 。</p>
|
||||
<h2 id="622">6.2.2 开放寻址<a class="headerlink" href="#622" title="Permanent link">¶</a></h2>
|
||||
<p>「开放寻址 open addressing」不引入额外的数据结构，而是通过“多次探测”来处理哈希冲突，探测方式主要包括线性探测、平方探测、多次哈希等。</p>
|
||||
<h3 id="1">1. 线性探测<a class="headerlink" href="#1" title="Permanent link">¶</a></h3>
|
||||
|
||||
@@ -1320,8 +1320,15 @@
|
||||
<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
|
||||
|
||||
<li class="md-nav__item">
|
||||
<a href="#641-q-a" class="md-nav__link">
|
||||
6.4.1 Q & A
|
||||
<a href="#1" class="md-nav__link">
|
||||
1. 重点回顾
|
||||
</a>
|
||||
|
||||
</li>
|
||||
|
||||
<li class="md-nav__item">
|
||||
<a href="#2-q-a" class="md-nav__link">
|
||||
2. Q & A
|
||||
</a>
|
||||
|
||||
</li>
|
||||
@@ -3398,8 +3405,15 @@
|
||||
<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
|
||||
|
||||
<li class="md-nav__item">
|
||||
<a href="#641-q-a" class="md-nav__link">
|
||||
6.4.1 Q & A
|
||||
<a href="#1" class="md-nav__link">
|
||||
1. 重点回顾
|
||||
</a>
|
||||
|
||||
</li>
|
||||
|
||||
<li class="md-nav__item">
|
||||
<a href="#2-q-a" class="md-nav__link">
|
||||
2. Q & A
|
||||
</a>
|
||||
|
||||
</li>
|
||||
@@ -3428,6 +3442,7 @@
|
||||
|
||||
|
||||
<h1 id="64">6.4 小结<a class="headerlink" href="#64" title="Permanent link">¶</a></h1>
|
||||
<h3 id="1">1. 重点回顾<a class="headerlink" href="#1" title="Permanent link">¶</a></h3>
|
||||
<ul>
|
||||
<li>输入 <code>key</code> ，哈希表能够在 <span class="arithmatex">\(O(1)\)</span> 时间内查询到 <code>value</code> ，效率非常高。</li>
|
||||
<li>常见的哈希表操作包括查询、添加键值对、删除键值对和遍历哈希表等。</li>
|
||||
@@ -3443,7 +3458,7 @@
|
||||
<li>常见的哈希算法包括 MD5、SHA-1、SHA-2 和 SHA3 等。MD5 常用于校验文件完整性，SHA-2 常用于安全应用与协议。</li>
|
||||
<li>编程语言通常会为数据类型提供内置哈希算法，用于计算哈希表中的桶索引。通常情况下，只有不可变对象是可哈希的。</li>
|
||||
</ul>
|
||||
<h2 id="641-q-a">6.4.1 Q & A<a class="headerlink" href="#641-q-a" title="Permanent link">¶</a></h2>
|
||||
<h3 id="2-q-a">2. Q & A<a class="headerlink" href="#2-q-a" title="Permanent link">¶</a></h3>
|
||||
<div class="admonition question">
|
||||
<p class="admonition-title">哈希表的时间复杂度为什么不是 <span class="arithmatex">\(O(n)\)</span> ？</p>
|
||||
<p>当哈希冲突比较严重时，哈希表的时间复杂度会退化至 <span class="arithmatex">\(O(n)\)</span> 。当哈希函数设计的比较好、容量设置比较合理、冲突比较平均时，时间复杂度是 <span class="arithmatex">\(O(1)\)</span> 。我们使用编程语言内置的哈希表时，通常认为时间复杂度是 <span class="arithmatex">\(O(1)\)</span> 。</p>
|
||||
|
||||
Reference in New Issue
Block a user