简单题

#include 
      
        #include 
       
         #include 
        
          #include 
         
           using namespace std; #define maxn 1005 int f[maxn]; int n; bool vis[maxn]; int gcd(int x, int y) {
     if (!x || !y) return x > y ? x : y; for (int t; t = x %y; x = y, y = t); return y; } int main() {
     //freopen("t.txt", "r", stdin);     scanf("%d", &n); for (int i = 0; i< n; i++)     {
     int a;         scanf("%d", &a);         a--;         f[a] = i;     }     memset(vis, 0, sizeof(vis)); int ans = 1; for (int i = 0; i < n; i++) if (!vis[i])         {
     int a = i; int b = 0; while (!vis[a])             {
                     vis[a] = true;                 a = f[a];                 b++;             }             ans = ans / gcd(ans, b) * b;         }     printf("%d\n", ans); return 0; }