20分垃圾蒟蒻求助

2-SAT问题模板，请问各位大佬哪错了

#include<bits/stdc++.h>
using namespace std;
vector<int>g[2000005];
stack<int>s;
int t,n,m,ind,cnt,dfn[2000005],low[2000005],scc[2000005];
char x[2],y[2];
bool f,vis[2000005];
void clean(){
    for(int i=1;i<=n;i++)g[i].clear();
    while(!s.empty())s.pop();
    ind=cnt=f=0;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(scc,0,sizeof(scc));
    memset(vis,0,sizeof(vis));
}
void tarjan(int u){
    dfn[u]=low[u]=++ind;
    s.push(u);
    vis[u]=1;
    for(int i=0;i<g[u].size();i++){
        int v=g[u][i];
        if(!dfn[v])tarjan(v),low[u]=min(low[u],low[v]);
        else if(vis[v])low[u]=min(low[u],dfn[v]);
    }
    if(dfn[u]==low[u]){
        cnt++;
        int v;
        do{
            v=s.top();
            s.pop();
            scc[v]=cnt;
            vis[v]=0;
        }while(u!=v);
    }
}
int main(){
    scanf("%d",&t);
    while(t--){
        clean();
        scanf("%d%d",&n,&m);
        for(int i=1;i<=m;i++){
            scanf("%s %s",x,y);
            if(x[0]=='m'&&y[0]=='m')g[x[1]-'0'+n].push_back(y[1]-'0'),g[y[1]-'0'+n].push_back(x[1]-'0');
            if(x[0]=='m'&&y[0]=='h')g[x[1]-'0'+n].push_back(y[1]-'0'+n),g[y[1]-'0'].push_back(x[1]-'0');
            if(x[0]=='h'&&y[0]=='m')g[x[1]-'0'].push_back(y[1]-'0'),g[y[1]-'0'+n].push_back(x[1]-'0'+n);
            if(x[0]=='h'&&y[0]=='h')g[x[1]-'0'].push_back(y[1]-'0'+n),g[y[1]-'0'].push_back(x[1]-'0'+n);
        }
        for(int i=1;i<=2*n;i++)if(!dfn[i])tarjan(i);
        for(int i=1;i<=n;i++){
            if(scc[i]==scc[i+n]){
                f=1;
                break;
            }
        }
        if(!f)printf("GOOD\n");
        else printf("BAD\n");
    }
}