PolandBall and Forest

題目： PolandBall and Forest

思路：本題就是一個簡單的並查集
並查集參考博客：並查集（Disjoint Set Union）
代碼：

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e4+10;
int fa[maxn];
int Find(int x){
     if(x != fa[x])fa[x] = Find(fa[x]);
     return fa[x];
}
int main(){
    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)fa[i] = i;
    for(int i = 1; i <= n; i++){
        int v;
        scanf("%d", &v);
        int fx, fy;
        fx = Find(i);
        fy = Find(v);
        if(fx != fy)fa[fx] = fy;
    }
    int ans  = 0;
    for(int i = 1; i <= n; i++){
        if(fa[i] == i)ans++;
    }
    printf("%d\n", ans);
return 0;
}