P2661 信息传递（并查集）

#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5 + 5;
int fa[maxn];
int cnt,n,a,ans = 0x3f3f3f3f;
int find(int x,int &cnt){
    cnt++;
    if(x == fa[x])
        return x;
    return find(fa[x],cnt);
}
int main(){
   // freopen("in","r",stdin);
    ios::sync_with_stdio(0);
    cin >> n;
    for(int i = 1; i <= n; i++)
        fa[i] = i;
    for(int i = 1; i <= n; i++){
        cin >> a;
        cnt = 0;
        if(find(a,cnt) == i)
            ans = min(ans,cnt);
        else fa[i] = a;
    }
    cout << ans;
    return 0;
}