thanksone's TIOJ 1149

#include <bits/stdc++.h>
using namespace std;
int cnt;
array<vector<int>, 35> G, B, S;
array<int, 35> scc, P, in, R;
array<bool, 35> vis;
void dfsb(int pos){
    vis[pos] = 1;
    for(int v : B[pos]){
        if(!vis[v]) dfsb(v);
    }
    P[++cnt] = pos;
}
void dfs(int pos){
    vis[pos] = 1;
    scc[pos] = cnt;
    for(int v : G[pos]){
        if(!vis[v]) dfs(v);
    }
}
signed main(){
    cin.tie(0), cout.tie(0), ios::sync_with_stdio(0);
    int t, n, m, u, v;
    bool ans;
    char a, b;
    cin >> t;
    while(t--){
        ans = 1;
        cin >> n >> m;
        for(int i = 2; i <= 2 * n + 1; i++){
            G[i].clear();
            B[i].clear();
        }
        for(int i = 1; i <= m; i++){
            cin >> a >> u >> b >> v;
            u *= 2;
            v *= 2;
            if(a == 'm') u++;
            if(b == 'm') v++;
            G[u ^ 1].push_back(v);
            G[v ^ 1].push_back(u);
            B[v].push_back(u ^ 1);
            B[u].push_back(v ^ 1);
        }
        cnt = 0;
        for(int i = 2; i <= 2 * n + 1; i++) vis[i] = 0;
        for(int i = 2; i <= 2 * n + 1; i++){
            if(!vis[i]) dfsb(i);
        }
        cnt = 0;
        for(int i = 2; i <= 2 * n + 1; i++) vis[i] = 0;
        for(int i = 2 * n; i > 0; i--){
            if(!vis[P[i]]){
                cnt++;
                dfs(P[i]);
            }
        }
        for(int i = 1; i <= n; i++){
            if(scc[2 * i] && scc[2 * i] == scc[2 * i + 1]) ans = 0;
        }
        cout << (ans? "GOOD\n" : "BAD\n");
    }
    return 0;
}