141. 周期(KMP）

https://www.acwing.com/problem/content/143/

 

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6 + 5;
char a[maxn];
int n,t;
int nxt[maxn];
void calc_next(){
    nxt[1] = 0;
    for(int i = 2, j = 0; i <= n; i++){
        while(j > 0 && a[i] != a[j + 1])
            j = nxt[j];
        if(a[i] == a[j + 1])
            j++;
        nxt[i] = j;
    }
}
int main(){
    while(cin >> n && n){
        scanf("%s",a + 1);
        calc_next();
        printf("Test case #%d\n",++t);
        for(int i = 2; i <= n; i++){
            if(i % (i - nxt[i]) == 0 && i / (i - nxt[i]) > 1){
                printf("%d %d\n",i,i / (i - nxt[i]));
            }
        }
        puts("");
    }
    return 0;
}