poj 1182（并查集，压缩路径，循环吃的标志）

#include<iostream>
#include<cstring>
using namespace std;
int n,d,x,y,num = 0;
struct node{
    int parent;
    int relation;
}point[50005];

int find_par(int x){
    if(point[x].parent==x)
        return x;
    int tmp = point[x].parent;
    point[x].parent = find_par(tmp);
    point[x].relation = (point[x].relation+point[tmp].relation)%3;
    return point[x].parent;
}
int main(){
    int k;
    scanf("%d%d",&n,&k);
    for(int i=1;i<n+1;i++){
        point[i].parent = i;
        point[i].relation = 0;
    }
    while(k--){
        scanf("%d%d%d",&d,&x,&y);
        if(x>n||y>n){
            num++;
            continue;
        }
        if(d==2&&x==y){
            num++;
            continue;
        }
        int px = find_par(x);
        int py = find_par(y);
        if(px!=py){
            point[px].parent = py;
            point[px].relation = (d-1+point[y].relation-point[x].relation+3)%3;
        }
        else{
            if(d==1&&point[x].relation!=point[y].relation){
                num++;
                continue;
            }
            if(d==2&&(point[x].relation-point[y].relation+3)%3!=1){
                num++;
                continue;
            }
        }
    }
    printf("%d\n",num);
    return 0;
}