hdu3068 maacher算法

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int M=250005;
int len,id,p[M],ans;
char s[M];
int main()
{
    while(scanf("%s",s)!=EOF){
        memset(p,0,sizeof(p));
        len=strlen(s); ans=1; id=0;
        for(int i=len;i>=0;i--) s[i*2+2]=s[i],s[i*2+1]=‘#‘;
        s[0]=‘&‘; len=len*2+1;
        for(int i=2;i<=len;i++){
            if(id+p[id]>i) p[i]=min(p[id*2-i],id+p[id]-i);
            else p[i]=1;
            while(s[i-p[i]]==s[i+p[i]]) p[i]++;
            if(p[i]>ans) ans=p[i];
            if(id+p[id]<i+p[i]) id=i;
        }
        printf("%d\n",ans-1);
    }
    return 0;
}