hiho一下第133周 2-SAT·hihoCoder音乐节(2-SAT)(强连通)

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <time.h>
#include <string>
#include <map>
#include <stack>
#include <vector>
#include <set>
#include <queue>
#define met(a,b) memset(a,b,sizeof a)
#define pb push_back
using namespace std;
const int N=2e3+50;
const int M=N*N+10;
int  n,m,k,s,t,tot,cut=0,tim=0,top=0;
int head[N],vis[N];
int dfn[N],low[N],stack1[N],num[N];
struct man {
    int to,next;
} edg[M];
void add(int u,int v) {
    //printf("!!!%d %d\n",u,v);
    edg[tot].to=v;
    edg[tot].next=head[u];
    head[u]=tot++;
}
void Tarjan(int u) {
    int v;
    low[u] = dfn[u] = ++tim;
    stack1[top++] = u;
    vis[u] = 1;
    for(int e = head[u]; e != -1; e = edg[e].next) {
        v = edg[e].to;
        if(!dfn[v]) {
            Tarjan(v);
            low[u] = min(low[u], low[v]);
        } else if(vis[v]) {
            low[u] = min(low[u], dfn[v]);
        }
    }
    if(low[u] == dfn[u]) {
        cut++;
        do {
            v = stack1[--top];
            num[v] = cut;
            vis[v] = 0;
        } while(u != v);
    }
}
void init(){
    tot=top=cut=tim=0;
    met(head,-1);
    met(low,0);
    met(dfn,0);met(vis,0);met(num,0);
}
int main() {
    int t,A,B;
    char a,b;
    scanf("%d",&t);
    while(t--){
        init();
        bool ok=true;
        scanf("%d%d",&n,&m);
        while(m--){
            scanf(" %c%d %c%d",&a,&A,&b,&B);
            int An=A+n;
            int Bn=B+n;
            if(a==‘h‘)swap(A,An);
            if(b==‘h‘)swap(B,Bn);
            add(An,B);add(Bn,A);
        }
        for(int i=1;i<=2*n;i++)if(!dfn[i])Tarjan(i);
        for(int i=1;i<=n;i++){
            if(num[i]==num[i+n]){
                ok=false;
                break;
            }
        }
        if(ok)puts("GOOD");
        else puts("BAD");
    }
    return 0;
}