poj3678 Katu Puzzle

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int n, m, hea[2005], cnt, scc, ind, dfn[2005], loo[2005], bel[2005];
int uu, vv, ww, sta[2005], din;
bool ins[2005];
char c[15];
struct Edge{
    int too, nxt;
}edge[4000005];
void add_edge(int fro, int too){
    edge[++cnt].nxt = hea[fro];
    edge[cnt].too = too;
    hea[fro] = cnt;
}
void tarjan(int u){
    sta[++din] = u;
    ins[u] = true;
    dfn[u] = loo[u] = ++ind;
    for(int i=hea[u]; i; i=edge[i].nxt){
        int t=edge[i].too;
        if(!dfn[t]){
            tarjan(t);
            loo[u] = min(loo[u], loo[t]);
        }
        else if(ins[t]) loo[u] = min(loo[u], dfn[t]);
    }
    int j;
    if(dfn[u]==loo[u]){
        scc++;
        do{
            j = sta[din--];
            ins[j] = false;
            bel[j] = scc;
        }while(dfn[j]!=loo[j]);
    }
}
int main(){
    cin>>n>>m;
    for(int i=1; i<=m; i++){
        scanf("%d %d %d", &uu, &vv, &ww);
        scanf("%s", c);
        uu *= 2; vv *= 2;
        if(c[0]==‘A‘){
            if(ww){
                add_edge(uu, vv); add_edge(vv, uu);
                add_edge(uu^1, uu); add_edge(vv^1, vv);//只要敢不选就让它矛盾
            }
            else
                add_edge(uu, vv^1), add_edge(vv, uu^1);
        }
        if(c[0]==‘O‘){
            if(ww)
                add_edge(uu^1, vv), add_edge(vv^1, uu);
            else{
                add_edge(uu, uu^1); add_edge(vv, vv^1);
                add_edge(uu^1, vv^1); add_edge(vv^1, uu^1);
            }
        }
        if(c[0]==‘X‘){
            if(ww){
                add_edge(uu, vv^1); add_edge(vv, uu^1);
                add_edge(vv^1, uu); add_edge(uu^1, vv);
            }
            else{
                add_edge(uu, vv); add_edge(vv, uu);
                add_edge(uu^1, vv^1); add_edge(vv^1, uu^1);
            }
        }
    }
    for(int i=0; i<n+n; i++)
        if(!dfn[i])
            tarjan(i);
    for(int i=0; i<n+n; i+=2)
        if(bel[i]==bel[i^1]){
            printf("NO\n");
            return 0;
        }
    printf("YES\n");
    return 0;
}