Cod sursă (job #664030)

#include <bits/stdc++.h>

const int NMAX = 3e3 + 5, mod = 1e9 + 7;

int n, cnt, x[NMAX], y[NMAX], z[NMAX], t[NMAX], f[NMAX], in[NMAX], d[NMAX];
std :: vector < int > A[NMAX];

std :: ifstream fin("canibali.in");
std :: ofstream fout("canibali.out");

bool Empty() {
    for (int i = 1; i <= n; ++ i)
        if (f[i] == false)
            return false;

    return true;
}

void DFS(int node) {
    f[node] = true;

    for (int i = 0; i < A[node].size(); ++ i) {
        int u = A[node][i];

        if (f[u] == false && d[node] > 0) {
            d[node] --;

            DFS(u);
        }
    }

    return;
}

int main() {
    fin >> n;

    for (int i = 1; i <= n; ++ i)
        fin >> x[i] >> y[i] >> z[i] >> t[i];

    for (int i = 1; i <= n; ++ i)
        for (int j = 1; j <= n; ++ j)
            if (i != j && x[i] >= x[j] && y[i] >= y[j] && z[i] >= z[j] && t[i] >= t[j]) {
                A[i].push_back(j);
                in[j] ++;
            }

    for (int i = 1; i <= n; ++ i)
        d[i] = 2;

    while (!Empty()) {
        int arg;

        for (int i = 1; i <= n; ++ i)
            if (f[i] == false)
                arg = i;

        DFS(arg);
        ++ cnt;
    }

    fout << cnt;

    return 0;
}