Noi2001 食物链(扩展域并查集）

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
 
const int maxn=150000+10;
 
int fa[maxn];
 
//x是self,x+n是eat,x+n+n是eat;
 
int getfa(int x){
    if(x==fa[x]) return x;
    return fa[x]=getfa(fa[x]);
}
 
void _merge(int x,int y){
     int xx=getfa(x);
     int yy=getfa(y);
     fa[xx]=yy;
}
 
int main(){
    int n,m;
    int ans=0;
    int x,y,id;
    scanf("%d%d",&n,&m);
    for (int i=1;i<=3*n;i++) fa[i]=i;
    for (int i=1;i<=m;i++){
        scanf("%d%d%d",&id,&x,&y);
        if(x>n||y>n) {ans++;continue;}
        if(id==1){
            if(getfa(x)==getfa(y+n)||getfa(x+n)==getfa(y)) {ans++;continue;}
            else {
                _merge(x,y);
                _merge(x+n,y+n);
                _merge(x+n+n,y+n+n);
            }
        }
        else {
            if(x==y||getfa(x)==getfa(y)||getfa(x)==getfa(y+n)) {ans++;continue;}
            else {
                _merge(x,y+n+n);
                _merge(x+n+n,y+n);
                _merge(x+n,y);
            }
        }
    }
    printf("%d\n",ans);
return 0;
}