Submission #956702

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Source Code Expand

#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
 
using namespace std;
using ll = long long;
using ull = unsigned long long;
constexpr ll TEN(int n) { return (n==0) ? 1 : 10*TEN(n-1); }
 
const int MN = 100100;
vector<int> g[MN], rg[MN];
int used[MN];
int ec = 0;
array<ll, 3> visit;
bool err = false;
void dfs(int p, int c) {
    if (used[p] != -1) {
        if (used[p] != c) err = true;
        return;
    }
    used[p] = c;
    visit[c]++;
    for (int d: g[p]) {
        ec++;
        dfs(d, (c+1)%3);
    }
    for (int d: rg[p]) {
        dfs(d, (c+2)%3);
    }
}
 
int main() {
    fill_n(used, MN, -1);
    ios::sync_with_stdio(0);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b; a--; b--;
        g[a].push_back(b);
        rg[b].push_back(a);
    }
    ll sm = 0;
    for (int i = 0; i < n; i++) {
        if (used[i] != -1) continue;
        visit = {0, 0, 0};
        ec = 0;
        err = false;
        dfs(i, 0);
        if (err) {
            ll v = visit[0]+visit[1]+visit[2];
            sm += v*(v-1);
            sm += v;
        } else {
            if (min(min(visit[0], visit[1]), visit[2]) == 0) {
                sm += ec;
            } else {
                sm += visit[0]*visit[1];
                sm += visit[1]*visit[2];
                sm += visit[2]*visit[0];
            }
        }
    }
    cout << sm << endl;
    return 0;
}

Submission Info

Judge Result