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40 lines
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40 lines
2.3 KiB
HTML
<p>字典 <code>wordList</code> 中从单词 <code>beginWord</code><em> </em>和 <code>endWord</code> 的 <strong>转换序列 </strong>是一个按下述规格形成的序列<meta charset="UTF-8" /> <code>beginWord -> s<sub>1</sub> -> s<sub>2</sub> -> ... -> s<sub>k</sub></code>：</p>
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<ul>
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<li>每一对相邻的单词只差一个字母。</li>
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<li><meta charset="UTF-8" /> 对于 <code>1 <= i <= k</code> 时，每个<meta charset="UTF-8" /> <code>s<sub>i</sub></code> 都在<meta charset="UTF-8" /> <code>wordList</code> 中。注意， <code>beginWord</code><em> </em>不需要在<meta charset="UTF-8" /> <code>wordList</code> 中。<meta charset="UTF-8" /></li>
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<li><code>s<sub>k</sub> == endWord</code></li>
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</ul>
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<p>给你两个单词<em> </em><code>beginWord</code><em> </em>和 <code>endWord</code> 和一个字典 <code>wordList</code> ，返回 <em>从 <code>beginWord</code> 到 <code>endWord</code> 的 <strong>最短转换序列</strong> 中的 <strong>单词数目</strong></em> 。如果不存在这样的转换序列，返回 <code>0</code> 。</p>
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<p><strong>示例 1：</strong></p>
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<pre>
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<strong>输入：</strong>beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log","cog"]
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<strong>输出：</strong>5
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<strong>解释：</strong>一个最短转换序列是 "hit" -> "hot" -> "dot" -> "dog" -> "cog", 返回它的长度 5。
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</pre>
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<p><strong>示例 2：</strong></p>
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<pre>
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<strong>输入：</strong>beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log"]
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<strong>输出：</strong>0
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<strong>解释：</strong>endWord "cog" 不在字典中，所以无法进行转换。</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul>
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<li><code>1 <= beginWord.length <= 10</code></li>
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<li><code>endWord.length == beginWord.length</code></li>
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<li><code>1 <= wordList.length <= 5000</code></li>
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<li><code>wordList[i].length == beginWord.length</code></li>
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<li><code>beginWord</code>、<code>endWord</code> 和 <code>wordList[i]</code> 由小写英文字母组成</li>
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<li><code>beginWord != endWord</code></li>
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<li><code>wordList</code> 中的所有字符串 <strong>互不相同</strong></li>
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</ul>
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