int used[10000];
    queue <int> q;
    vector<int> p[10000];
    int num;
    bool bfs(int v, int colour, int start) {
        q.push(v);
        while (!q.empty()) {
            v = q.front();
            used[v] = colour;
            q.pop();
            for (int i = 0; i < p[v].size(); i++) {
                if (used[p[v][i]] == colour && p[v][i] == start) return false;
                if (used[p[v][i]] == colour) {
                    if (!bfs(p[v][i], -1, p[v][i])) return false;
                    for (int j = 0; j < num; j++) if (used[j] == -1) used[j] = colour;
                }
                if (used[p[v][i]] == 0 || colour == -1)q.push(p[v][i]);

            }
        }
        return true;
    }
    bool canFinish(int numCourses, vector<pair<int, int>>& pr) {
        num = numCourses;
        if (pr.size() == 0) return true;
        for (int i = 0; i < pr.size(); i++) {
            p[pr[i].second].push_back(pr[i].first);
        }
        bool ans = true;
        int cnt = 1;
        for (int i = 0; i < numCourses; i++) {
            if (used[i] == 0 && p[i].size() != 0) {
                ans = bfs(i, cnt, i);
                cnt++;
            }
            if (!ans) return false;
        }
        return true;
    }