UVALive 4975 Casting Spalls

//回文长度：p[i]-1
#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<iostream>
using namespace std;
const int maxn=300050;
char s[maxn*2];
int p[maxn*2];

void manachar()
{
int i,id=0,len=strlen(s);
for(i=len;i>=0;i--){
s[(i<<1)+2]=s[i];
s[(i<<1)|1]='#';
}
s[0]='^';
len=len*2+1;
for(i=2;i<len;i++)
{
if(p[id]+id>i) p[i]=min(p[(id<<1)-i],p[id]+id-i);
else p[i]=1;
while(s[i-p[i]] == s[i+p[i]]) p[i]++;
if(i+p[i]>id+p[id]) id=i;
}
}

int main()
{
int T;
scanf("%d",&T);
while(T--)
{
scanf("%s",s);
manachar();
int ans=0,h;
for(int i=3;i<len;i+=2){
int M=p[i]-1;
M=(M>>2)<<2;
for(;M>ans;M-=4)
{
h=M>>1;
if(p[i+h]<(M>>1)) continue;
if(p[i-h]<(M>>1)) continue;
ans=M; break;
}
}
printf("%d\n",ans);
}
return 0;
}