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chapter_hashing/hash_map/index.html
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@@ -4196,7 +4196,7 @@
<p>输入一个 <code>key</code> ，哈希函数的计算过程分为以下两步。</p>
<ol>
<li>通过某种哈希算法 <code>hash()</code> 计算得到哈希值。</li>
<li>将哈希值对桶数量（数组长度）<code>capacity</code> 取模，从而获取该 <code>key</code> 对应的数组索引 <code>index</code> 。</li>
<li>将哈希值对桶数量（数组长度）<code>capacity</code> 取模，从而获取该 <code>key</code> 对应的桶（数组索引）<code>index</code> 。</li>
</ol>
<div class="highlight"><pre><span></span><code><a id="__codelineno-28-1" name="__codelineno-28-1" href="#__codelineno-28-1"></a><span class="nv">index</span><span class="w"> </span><span class="o">=</span><span class="w"> </span>hash<span class="o">(</span>key<span class="o">)</span><span class="w"> </span>%<span class="w"> </span>capacity
</code></pre></div>
@@ -4229,7 +4229,7 @@
<a id="__codelineno-29-18" name="__codelineno-29-18" href="#__codelineno-29-18"></a> <span class="n">index</span> <span class="o">=</span> <span class="n">key</span> <span class="o">%</span> <span class="mi">100</span>
<a id="__codelineno-29-19" name="__codelineno-29-19" href="#__codelineno-29-19"></a> <span class="k">return</span> <span class="n">index</span>
<a id="__codelineno-29-20" name="__codelineno-29-20" href="#__codelineno-29-20"></a>
<a id="__codelineno-29-21" name="__codelineno-29-21" href="#__codelineno-29-21"></a> <span class="k">def</span><span class="w"> </span><span class="nf">get</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">:</span> <span class="nb">int</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">str</span><span class="p">:</span>
<a id="__codelineno-29-21" name="__codelineno-29-21" href="#__codelineno-29-21"></a> <span class="k">def</span><span class="w"> </span><span class="nf">get</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">:</span> <span class="nb">int</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">str</span> <span class="o">|</span> <span class="kc">None</span><span class="p">:</span>
<a id="__codelineno-29-22" name="__codelineno-29-22" href="#__codelineno-29-22"></a><span class="w"> </span><span class="sd">&quot;&quot;&quot;查询操作&quot;&quot;&quot;</span>
<a id="__codelineno-29-23" name="__codelineno-29-23" href="#__codelineno-29-23"></a> <span class="n">index</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">hash_func</span><span class="p">(</span><span class="n">key</span><span class="p">)</span>
<a id="__codelineno-29-24" name="__codelineno-29-24" href="#__codelineno-29-24"></a> <span class="n">pair</span><span class="p">:</span> <span class="n">Pair</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">]</span>
@@ -4238,7 +4238,7 @@
<a id="__codelineno-29-27" name="__codelineno-29-27" href="#__codelineno-29-27"></a> <span class="k">return</span> <span class="n">pair</span><span class="o">.</span><span class="n">val</span>
<a id="__codelineno-29-28" name="__codelineno-29-28" href="#__codelineno-29-28"></a>
<a id="__codelineno-29-29" name="__codelineno-29-29" href="#__codelineno-29-29"></a> <span class="k">def</span><span class="w"> </span><span class="nf">put</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">:</span> <span class="nb">int</span><span class="p">,</span> <span class="n">val</span><span class="p">:</span> <span class="nb">str</span><span class="p">):</span>
<a id="__codelineno-29-30" name="__codelineno-29-30" href="#__codelineno-29-30"></a><span class="w"> </span><span class="sd">&quot;&quot;&quot;添加操作&quot;&quot;&quot;</span>
<a id="__codelineno-29-30" name="__codelineno-29-30" href="#__codelineno-29-30"></a><span class="w"> </span><span class="sd">&quot;&quot;&quot;添加和更新操作&quot;&quot;&quot;</span>
<a id="__codelineno-29-31" name="__codelineno-29-31" href="#__codelineno-29-31"></a> <span class="n">pair</span> <span class="o">=</span> <span class="n">Pair</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">val</span><span class="p">)</span>
<a id="__codelineno-29-32" name="__codelineno-29-32" href="#__codelineno-29-32"></a> <span class="n">index</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="bp">self</span><span class="o">.</span><span class="n">hash_func</span><span class="p">(</span><span class="n">key</span><span class="p">)</span>
<a id="__codelineno-29-33" name="__codelineno-29-33" href="#__codelineno-29-33"></a> <span class="bp">self</span><span class="o">.</span><span class="n">buckets</span><span class="p">[</span><span class="n">index</span><span class="p">]</span> <span class="o">=</span> <span class="n">pair</span>

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chapter_hashing/summary/index.html
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@@ -3678,6 +3678,8 @@
<p>查找的时候通过哈希函数找到对应的桶和键值对，发现 <code>key</code> 不匹配，这就代表有哈希冲突。因此，线性探测法会根据预先设定的步长依次向下查找，直至找到正确的键值对或无法找到跳出为止。</p>
<p><strong>Q</strong>：为什么哈希表扩容能够缓解哈希冲突？</p>
<p>哈希函数的最后一步往往是对数组长度 <span class="arithmatex">\(n\)</span> 取模（取余），让输出值落在数组索引范围内；在扩容后，数组长度 <span class="arithmatex">\(n\)</span> 发生变化，而 <code>key</code> 对应的索引也可能发生变化。原先落在同一个桶的多个 <code>key</code> ，在扩容后可能会被分配到多个桶中，从而实现哈希冲突的缓解。</p>
<p><strong>Q</strong>：如果为了高效的存取，那么直接使用数组不就好了吗？</p>
<p>当数据的 <code>key</code> 是连续的小范围整数时，直接用数组即可，简单高效。但当 <code>key</code> 是其他类型（例如字符串）时，就需要借助哈希函数将 <code>key</code> 映射为数组索引，再通过桶数组存储元素，这样的结构就是哈希表。</p>
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