学习建图
#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;
}