pku 1182(种类并查集)

题目链接：http://poj.org/problem?id=1182

解题思路来自discuss:http://poj.org/showmessage?message_id=152847

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 50050
int parent[MAXN];
int kind[MAXN];
int n,m,tag;

void Initiate()
{
    for(int i=0;i<=n;i++){
        parent[i]=i;
    }
    memset(kind,0,(n+2)*sizeof(kind[0]));
}

int Find(int x)
{
    if(x==parent[x]){
        return parent[x];
    }
    int tmp=Find(parent[x]);
    kind[x]=(kind[x]+kind[parent[x]])%3;
    return parent[x]=tmp;
}

void Union(int a,int b)
{
    int r1=Find(a),r2=Find(b);
    parent[r1]=r2;
    kind[r1]=(kind[b]-kind[a]+3+tag-1)%3;
}


int main()
{
  //  freopen("1.txt","r",stdin);
    int a,b,ans=0;
    scanf("%d%d",&n,&m);
    Initiate();
    while(m--){
        scanf("%d%d%d",&tag,&a,&b);
        if(a>n||b>n||(tag==2&&a==b)){ ans++;continue; }
        if(Find(a)!=Find(b)){
            Union(a,b);
        }else {
            if((kind[a]-kind[b]+3)%3!=(tag-1))
                ans++;
        }
    }
    printf("%d
",ans);
    return 0;
}