最长回文子串

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<queue>
#include<vector>
#include<cstring>
#include<cmath>
#include<map>
using namespace std;
typedef long long ll;
#define N 2011111
char s1[N],s[N];
int p[N],len;
void init()
{
    for(int i=0; i<len; i++){
        s[i*2]='*';
        s[i*2+1]=s1[i];
    }
    s[len*2]='*';
    len=len*2+1;
}
int sk()
{
    int mx=-1,id,ss=-1;
    for(int i=0;i<len;i++){
        if(mx>i)p[i]=min(p[2*id-i],mx-i);
        else p[i]=1;
        while(s[i-p[i]]==s[i+p[i]]&&i-p[i]>=0&&i+p[i]<len)p[i]++;
        if(mx<i+p[i]){
            mx=i+p[i];
            id=i;
        }
        ss=max(ss,p[i]);
    }
    //for(int i=0;i<len;i++)printf("%3c",s[i]);cout<<endl;
    //for(int i=0;i<len;i++)printf("%3d",p[i]);cout<<endl;
    return ss-1;
}
int main()
{
    int n;
    scanf("%d",&n);
    while(n--){
        scanf("%s",&s1);
        len=strlen(s1);
        init();
        printf("%d\n",sk());
    }
    return 0;
}