50分求助

我尽力了

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <stack>
#define maxn 2100
using namespace std;
vector<int > G[maxn];
int dfn[maxn], low[maxn], vis[maxn], color[maxn];
int T, n, m, num, tot;
stack<int> S;
void add(int x, int a, int y, int b) {
    x = x * 2 + a;
    y = y * 2 + b;
    G[x^1].push_back(y);
    G[y^1].push_back(x);
}
void init() {
    for (int i = 0; i <= maxn; i++) G[i].clear();
    memset(dfn, 0, sizeof(dfn));
    memset(low, 0, sizeof(low));
    memset(vis, 0, sizeof(vis));
    memset(color, 0, sizeof(color));
    num = 0;
    tot = 0;
    while (!S.empty()) S.pop();
}
void Tarjan(int x) {
    dfn[x] = low[x] = ++num;
    vis[x] = 1;
    S.push(x);
    for (int i = 0; i < G[x].size(); i++) {
        int y = G[x][i];
        if (!dfn[y]) {
            Tarjan(y);
            low[x] = min(low[x], low[y]);
        }
        else if (vis[y]) {
            low[x] = min(low[x], dfn[y]);
        }
    }
    if (dfn[x] == low[x]) {
        int y = S.top(); S.pop();
        color[x] = ++tot;
        vis[x] = 0;
        while (x != y) {
            color[y] = tot;
            y = S.top(); S.pop();
            vis[y] = 0;
        }
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> T;
    while (T--) {
        init();
        cin >> n >> m;
        string s1, s2;
        int x, a, y, b;
        for (int i = 0; i < m; i++) {
            cin >> s1 >> s2;
            if (s1[0] == 'h') a = 0;
            else a = 1;
            if (s2[0] == 'h') b = 0;
            else b = 1;
            x = s1[1] - '1';
            y = s2[1] - '1';
            add(x, a, y, b);
        }
        for (int i = 0; i < n * 2; i++) {
            if (!dfn[i]) Tarjan(i);
        }
        bool bj = 1;
        for (int i = 0; i < n; i++) {
            if (color[i * 2] == color[i * 2 + 1]) {
                bj = 0;
                break;
            }
        }
        if (bj) cout << "GOOD" << endl;
        else cout << "BAD" << endl;
    }
    return 0;
}