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:

 1 #include<iostream>
 2 #include<cstdio>
 3 
 4 using namespace std;
 5 
 6 int n,j,next[1000001];
 7 string l,p; 
 8 
 9 int main() {
10     scanf("%d",&n);
11     l = " ";
12     cin >> p;
13     l += p;
14     next[1] = 0;
15     for(int i = 2;i <= n; i++) {
16         while(j != 0 && l[i] != l[j+1]) j = next[j];
17         if(l[i] == l[j+1]) j++;
18         next[i] = j;
19     }
20     printf("%d",n - next[n]);
21     return 0;
22 }