提出 #71748638

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ソースコード 拡げる

#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define all(v) v.begin(), v.end()
#define memo(v, x) memset(v, x, sizeof(v))
#define sz(v) (int)v.size()

void solve() {
    int n; cin >> n;
    vector<int> v(n + 1);
    for (int i = 1; i <= n; i++) cin >> v[i];
    ll ans = 0;
    vector<int> vis(n + 1);
    function<ll(int)> go = [&](int i) -> ll {
        if (vis[i]) return 1;
        vis[i] = 1;
        return 1 + go(v[i]);
    };
    for (int i = 1; i <= n; i++) {
        ll c = go(i) - 1;
        ans += (c * (c - 1) / 2);
    }
    cout << ans << '\n';
}

int main() {
    cin.tie(0) -> sync_with_stdio(0);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int tc = 1;
    // cin >> tc;
    for (int t = 1; t <= tc; t++) {
        solve();
    }
    return 0;
}

提出情報

ジャッジ結果