提出 #71686307

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ソースコード 拡げる

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vmi = vector<mint>;
using vvmi = vector<vmi>;
using vvvmi = vector<vvmi>;
#define all(a) (a).begin(), (a).end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)

ll op(ll a, ll b){
    return a+b;
}
ll e(){return 0;}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n; cin >> n;
    vi p(n); rep(i, n)cin >> p[i];
    rep(i, n)p[i]--;
    scc_graph scc(n);
    rep(i, n)scc.add_edge(i, p[i]);
    vvi g = scc.scc();
    ll ans = 0;
    for(auto v : g){
        
        ll s = v.size();
        ans += s*(s-1)/2;
    }cout << ans << endl;
    /*segtree<ll, op, e> seg(n);
    ll k = 0;
    rep(i, n){
        k += seg.prod(p[i]+1, n);
        seg.set(p[i], 1);
    }
    cout << k << endl;*/

    
    return 0;
}

提出情報

ジャッジ結果