37 lines
1.3 KiB
JavaScript
37 lines
1.3 KiB
JavaScript
export const longestPalindrome = function (s) {
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if (!s || !s.trim()) return ''
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if (s.length === 1) return s
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if (s.length === 2) return s[0] === s[1] ? s[0] + s[1] : s[1]
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let result = ''
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/**
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*扩散坐标
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*/
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const calPalindromeIndex = function (left, right, s) {
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const len = s.length
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while (left >= 0 && right < len && s[left] === s[right]) {
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left--
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right++
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}
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return { left: left + 1, right: right }
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}
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for (let i = 0, len = s.length; i < len; i++) {
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let even = ''
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let odd = ''
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if (s[i] === s[i + 1]) {
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// 经过当前位与下一位判断已构成回文，扩散位直接从下一位开始，可以提速
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const evenIndex = calPalindromeIndex(i - 1, i + 2, s)
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even = s.slice(evenIndex.left, evenIndex.right)
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}
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const oddIndex = calPalindromeIndex(i - 1, i + 1, s)
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odd = s.slice(oddIndex.left, oddIndex.right)
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const re = odd.length > even.length ? odd : even
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result = result.length > re.length ? result : re
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}
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return result
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}
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// 作者：liu-zi-qian-2
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// 链接：https://leetcode-cn.com/problems/longest-palindromic-substring/solution/5-zui-chang-hui-wen-zi-chuan-by-liu-zi-qian-2/
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// 来源：力扣（LeetCode）
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// 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
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