solve.cpp

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

int main() {
    int T;
    cin >> T;
    int u, v, src, dst;
    while (T--) {
        int n, m;
        cin >> n >> m;
        vector<vector<int>> adj(n);
        for (int i = 0; i < m; i++) {
            cin >> u >> v;
            adj[u].push_back(v);
        }
        cin >> src >> dst;
        vector<bool> visited(n, false);
        visited[src] = true;
        // maintain a queue of pairs <node, dist>, pop when dist > 6 until queue is empty
        queue<pair<int, int>> q;
        q.push({src, 0});
        bool hasPath = false;
        while (!q.empty()) {
            pair<int, int> p = q.front();
            q.pop();
            if (p.first == dst) {
                hasPath = true;
                break;
            }
            if (p.second >= 6) {
                continue;
            }
            for (const auto next : adj[p.first]) {
                if (!visited[next]) {
                    visited[next] = true;
                    q.push({next, p.second + 1});
                }
            }
        }
        if (hasPath) {
            cout << "YES\n";
        } else {
            cout << "NO\n";
        }
    }
    return 0;
}