每日一刷之leetcode 最长回文子串

最长回文子串

每天刷1题, 纯属个人兴趣爱好

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一、题目描述

二、解题步骤

class Solution {
public:
    pair<int, int> expand(const string &s, int left, int right) {
        while (left >= 0 && right < s.size() && s[left] == s[right]) {
            --left;
            ++right;
        }
        return {left+1, right-1};
    }

    string longestPalindrome(string s) {
        int start = 0, end =0;
        for (int i = 0; i < s.size(); i++) {
            auto [left1, right1] = expand(s, i, i);
            auto [left2, right2] = expand(s, i, i + 1);

            if (right1 - left1 > end - start) {
                start = left1;
                end = right1;
            }

            if (right2 - left2 > end - start) {
                start = left2;
                end = right2;
            }
        }
        return s.substr(start, end - start + 1);
    }
};

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三、执行结果