poj1961 period KMP求循环节

http://poj.org/problem?id=1961

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
int len,t;
char s[1000005];
int next[1000005];

int main(){
    while(1){
        scanf("%d",&len);
        if(len == 0)break;
        scanf("%s",s);

        printf("Test case #%d\n",++t);

        int i = 0,j = -1;
        next[0] = -1;
        while(i != len){
            if(j == -1 || s[i] == s[j]){
                next[++i] = ++j;
                if(i % (i - next[i]) == 0){
                    int k = i / (i - next[i]);
                    if(k>1)printf("%d %d\n",i,k);
                }
            }
            else j = next[j];
        }
        printf("\n");
    } 

    return 0;
}