最长回文子串：manacher算法

来源：互联网发布：mac打开远程桌面连接编辑：程序博客网时间：2024/06/07 19:44

主要思路是通过对称性简化运算。可以参照https://www.felix021.com/blog/read.php?2040

hdu3068：

#include <bits/stdc++.h>using namespace std;char str[150000], s[230000];int p[230000];inline int Min(int a, int b){ return a<b?a:b; }inline int Max(int a, int b){ return a>b?a:b; }int main(){    while (scanf("%s", str+1) != EOF) {        memset(s, 0, sizeof s);        s[0] = '*';        for (int i = 1, len = strlen(str+1), j = 1; i <= len; i++, j += 2)            s[j] = str[i], s[j+1] = '#';        int l = strlen(str+1)*2;        s[l] = '-';        int id = 0, maxl = 0;        for (int i = 1; i <= l; i++) {            if (id+p[id] >= i) p[i] = Min(id+p[id]-i, p[id*2-i]);            else p[i] = 0;            while (s[i+p[i]+1] == s[i-p[i]-1]) p[i]++;            if (i+p[i] >= id+p[id]) id = i;        }        for (int i = 1; i <= l; i++) {            if (s[i] == '#') maxl = Max(maxl, (p[i]+1)/2*2);            else maxl = Max(maxl, p[i]/2*2+1);        }        printf("%d\n", maxl);    }    return 0;}

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