Period

题目描述

For each prefix of a given string S with N characters (each character has an ASCII code between 97 and 126, inclusive), we want to know whether the prefix is a periodic string. That is, for each i (2 <= i <= N) we want to know the largest K > 1 (if there is one) such that the prefix of S with length i can be written as A K , that is A concatenated K times, for some string A. Of course, we also want to know the period K. 

输入描述:

The input file consists of several test cases. Each test case consists of two lines. The first one contains N (2 <= N <= 1 000 000) � the size of the string S. The second line contains the string S. The input file ends with a line, having the number zero on it.
       

输出描述:

For each test case, output “Test case #” and the consecutive test case number on a single line; then, for each prefix with length i that has a period K > 1, output the prefix size i and the period K separated by a single space; the prefix sizes must be in increasing order. Print a blank line after each test case.
       

示例1

输入

3
aaa
12
aabaabaabaab
0

输出

Test case #1
2 2
3 3

Test case #2
2 2
6 2
9 3
12 4

#include<stdio.h>
#include<string.h>
int next[1000005],n;
char s[1000005];
void getnext(char *s)
{
    int i,j;
    memset(next,0,sizeof(next));
    next[0]=-1;
    i=0;
    j=-1;
    while(i<n)
    {
        if(j==-1||s[i]==s[j])
        {
            i++;
            j++;
            next[i]=j;
        }
        else
            j=next[j];
    }
}
int main()
{
    int c=0;
    while(scanf("%d",&n)!=EOF,n)
    {
        int i;
        scanf("%s",s);
        getnext(s);
        printf("Test case #%d\n",++c);
        for(i=2;i<=n;i++)
        {
            int len=i-next[i];
            if(i%len==0&&i/len>1)
            {
                printf("%d %d\n",i,i/len);
            }
        }
        printf("\n");
    }
}