19.1.20 [LeetCode 5]Longest Palindromic Substring

Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

Example 1:

Input: "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:

Input: "cbbd"
Output: "bb"

class Solution {
public:
    string longestPalindrome(string s) {
        int leng = 0, size = s.length();
        string p;
        for (int i = 0; i<size; i++) {
            int l = 1;
            int S = i, E = i;
            while (S > 0 && E < size - 1 && s[S - 1] == s[E + 1]) {
                S--, E++;
                l += 2;
            }
            if (l > leng) {
                p = s.substr(S, l);
                leng = l;
            }
        }
        for (int i = 0; i < size-1; i++) {
            if (i + 1 > size - 1)break;
            int l = 0;
            int S = i+1, E = i;
            while (S > 0 && E < size - 1 && s[S - 1] == s[E + 1]) {
                S--, E++;
                l += 2;
            }
            if (l > leng) {
                p = s.substr(S, l);
                leng = l;
            }
        }
        return p;
    }
};

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