最长回文子串

给出一个只由小写英文字符a,b,c…y,z组成的字符串S,求S中最长回文串的长度.
回文就是正反读都是一样的字符串,如aba, abba等
Input
输入有多组case,不超过120组,每组输入为一行小写英文字符a,b,c…y,z组成的字符串S
两组case之间由空行隔开(该空行不用处理)
字符串长度len <= 110000
Output
每一行一个整数x,对应一组case,表示该组case的字符串中所包含的最长回文长度.
Sample Input
aaaa

abab
Sample Output
4
3

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;
#define ll long long int 
#define ull unsigned long long int 
#define e 2.718281828459
#define INF 0x7fffffff
#pragma warning(disable:4996)
#define pf printf
#define sf scanf
#define max(a,b) (a)>(b)?(a):(b);
#define min(a,b) (a)<(b)?(a):(b);
#define pi  acos(-1.0);
#define  eps 1e-9;
#include <cstdlib>
using namespace std;

char ar[110001];
char temp[220002];
int p[220002];
int manacher(int len) {
    int ans = 0;
    int j = 0;
    int id = 0;
    int mx = 0;
    for (int i = 1; i < len; i++) {
        if (i > mx) p[i] = 1;
        else p[i] =min( p[2 * id - i],mx-i);

        while (temp[i - p[i]] == temp[i + p[i]])
            p[i]++;

        if (i + p[i] > mx) {
            mx = i + p[i];
            id = i;;
        }
        if (ans < p[i])
            ans = p[i];

    }
    return ans;
}

void init(int len) {
    temp[0] = '@';
    temp[1] = '#';
    int j = 2;
    for (int i = 0; i < len; i++) {
        temp[j++] = ar[i];
        temp[j++] = '#';
    }
    temp[j] = '\0';
}

int main(void) {

    while (sf("%s", ar)!=EOF) {
        int n = strlen(ar);
        init(n);
        int maxlen = manacher(2 * n + 1);//2*n+1:除去最头和最尾
        pf("%d\n", maxlen-1);

    }
    return 0;
}