poj3974 Palindrome

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define N 2000050
char s[N],l[2*N];
int p[N],len;
int manacher()
{
    for(int i=1;i<=len;i++)
        p[i]=0;
    l[0]=‘!‘,l[1]=‘#‘;
    for(int i=1;i<=len;i++)
    {
        l[i<<1]=s[i];
        l[i<<1|1]=‘#‘;
    }
    l[(len<<1)+2]=‘*‘;
    int mx = 0,mid = 0,ret = 0;
    for(int i=1;i<=2*len+1;i++)
    {
        if(i<mx)p[i]=min(mx-i+1,p[mid*2-i]);
        else p[i]=1;
        while(l[i+p[i]]==l[i-p[i]])p[i]++;
        if(i+p[i]-1>mx)
        {
            mx=i+p[i]-1;
            mid = i;
        }
        ret = max(ret,p[i]-1);
    }
    return ret;
}
int main()
{
    int n = 0;
    while(scanf("%s",s+1))
    {
        len = strlen(s+1);
        if(s[1]==‘E‘&&s[2]==‘N‘&&s[3]==‘D‘&&len==3)break;
        n++;
        printf("Case %d: %d\n",n,manacher());
    }
    return 0;
}