Submission #1593966

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Source Code Expand

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

const int DIM = 1e5 + 5;

int col[DIM], cnt[3];
vector<pair<int, int>> edg[DIM];

void dfs(int x, int c, bool &ok, int &nrn, int &nre)
{
    ++cnt[c]; col[x] = c; ++nrn;
    
    for (pair<int, int> y : edg[x]) {
        if (y.second == 1)
            ++nre;
        if (col[y.first] == -1)
            dfs(y.first, (c + y.second + 3) % 3, ok, nrn, nre);
        if (col[y.first] != (c + y.second + 3) % 3)
            ok = false;
    }
    
    return;
}

int main(void)
{
    ios :: sync_with_stdio(false);
    cin.tie(); cout.tie();
    
    int n, m;
    cin >> n >> m;
    
    long long ans = m;
    for (int i = 1; i <= m; ++i) {
        int x, y;
        cin >> x >> y;
        
        edg[x].push_back(make_pair(y,  1));
        edg[y].push_back(make_pair(x, -1));
    }
    
    memset(col + 1, -1, n << 2);
    for (int i = 1; i <= n; ++i) {
        if (col[i] != -1) continue;
        bool ok = true; int nrn = 0, nre = 0;
        
        cnt[0] = cnt[1] = cnt[2] = 0;
        dfs(i, 0, ok, nrn, nre);
        
        if (!ok)
            ans += 1LL * nrn * nrn - nre;
        else
        if (cnt[0] and cnt[1] and cnt[2])
            ans += 1LL * cnt[0] * cnt[1] +
                   1LL * cnt[1] * cnt[2] +
                   1LL * cnt[2] * cnt[0] - nre;
    }
    
    cout << ans << endl;
    return 0;
}

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