LeetCode 5 Longest Palindromic Substring

题意：

最长回文子串

思路：

manacher裸题… = =！

代码：

//// Created by house on 1/9/17.//class Solution {public:    string longestPalindrome(string s) {        stringstream ss;        ss << "#";        for (char x:s) {            ss << x << "#";        }        ss << "#";        string f = ss.str();        int ans = 0, max_pos = 0;        int pos = 0, max_right = 0;        int pal[f.size()];        memset(pal, 0, sizeof(pal));        for (int i = 0; i < f.size(); ++i) {            if (i < max_right) {                pal[i] = min(pal[pos * 2 - i], max_right - i);            } else {                pal[i] = 1;            }            for (int j = pal[i] + 1; i - j + 1 >= 0 && i + j - 1 < f.size() && f[i - j + 1] == f[i + j - 1]; ++j) {                pal[i] = j;            }            if (i + pal[i] - 1 > max_right) {                max_right = i + pal[i] - 1;                pos = i;            }            if (pal[i] - 1 > ans) {                ans = pal[i] - 1;                max_pos = i;            }        }        printf("%d %d\n", max_pos, ans);        return s.substr((max_pos - pal[max_pos] + 1) / 2, ans);    }};