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13.2.2. &nbsp; 考虑重复的情况
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13.2.3. &nbsp; 复杂度分析
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13.3. &nbsp; n 皇后问题New
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13.2.2. &nbsp; 考虑重复的情况
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13.2.3. &nbsp; 复杂度分析
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<p><img alt="两种剪枝条件的作用范围" src="../permutations_problem.assets/permutations_ii_pruning_summary.png" /></p>
<p align="center"> Fig. 两种剪枝条件的作用范围 </p>
<h2 id="1323">13.2.3. &nbsp; 复杂度分析<a class="headerlink" href="#1323" title="Permanent link">&para;</a></h2>
<p>假设元素两两之间互不相同,则 <span class="arithmatex">\(n\)</span> 个元素共有 <span class="arithmatex">\(n!\)</span> 种排列(阶乘);在记录结果时,需要复制长度为 <span class="arithmatex">\(n\)</span> 的列表,使用 <span class="arithmatex">\(O(n)\)</span> 时间。因此,<strong>时间复杂度为 <span class="arithmatex">\(O(n!n)\)</span></strong></p>
<p>最大递归深度为 <span class="arithmatex">\(n\)</span> ,使用 <span class="arithmatex">\(O(n)\)</span> 栈帧空间。<code>selected</code> 使用 <span class="arithmatex">\(O(n)\)</span> 空间。同一时刻最多共有 <span class="arithmatex">\(n\)</span><code>duplicated</code> ,使用 <span class="arithmatex">\(O(n^2)\)</span> 空间。因此,<strong>全排列 I 的空间复杂度为 <span class="arithmatex">\(O(n)\)</span> ,全排列 II 的空间复杂度为 <span class="arithmatex">\(O(n^2)\)</span></strong></p>
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