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48 lines
1.8 KiB
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48 lines
1.8 KiB
HTML
<p>You are given a <strong>0-indexed</strong> array of <strong>unique</strong> strings <code>words</code>.</p>
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<p>A <strong>palindrome pair</strong> is a pair of integers <code>(i, j)</code> such that:</p>
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<ul>
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<li><code>0 <= i, j < words.length</code>,</li>
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<li><code>i != j</code>, and</li>
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<li><code>words[i] + words[j]</code> (the concatenation of the two strings) is a <span data-keyword="palindrome-string">palindrome</span>.</li>
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</ul>
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<p>Return <em>an array of all the <strong>palindrome pairs</strong> of </em><code>words</code>.</p>
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<p>You must write an algorithm with <code>O(sum of words[i].length)</code> runtime complexity.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> words = ["abcd","dcba","lls","s","sssll"]
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<strong>Output:</strong> [[0,1],[1,0],[3,2],[2,4]]
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<strong>Explanation:</strong> The palindromes are ["abcddcba","dcbaabcd","slls","llssssll"]
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> words = ["bat","tab","cat"]
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<strong>Output:</strong> [[0,1],[1,0]]
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<strong>Explanation:</strong> The palindromes are ["battab","tabbat"]
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> words = ["a",""]
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<strong>Output:</strong> [[0,1],[1,0]]
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<strong>Explanation:</strong> The palindromes are ["a","a"]
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= words.length <= 5000</code></li>
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<li><code>0 <= words[i].length <= 300</code></li>
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<li><code>words[i]</code> consists of lowercase English letters.</li>
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</ul>
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