洛谷 P4391 [BOI2009]Radio Transmission 无线传输

题目传送门

解题思路:

本题所要求的循环节,其实就是最长公共前缀的前缀长度减去前后缀重叠的一部分

AC代码:

#include<iostream>
#include<cstdio>

using namespace std;

int n,j,next[1000001];
string l,p; 

int main() {
    scanf("%d",&n);
    l = " ";
    cin >> p;
    l += p;
    next[1] = 0;
    for(int i = 2;i <= n; i++) {
        while(j != 0 && l[i] != l[j+1]) j = next[j];
        if(l[i] == l[j+1]) j++;
        next[i] = j;
    }
    printf("%d",n - next[n]);
    return 0;
}