poj1182 食物链【带权并查集】

题目链接：​​http://poj.org/problem?id=1182​​​
题意：中文题
解析：带权并查集，为每个元素创建三个元素，i-A,i-B,i-C，然后维护3*n个元素

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int maxn = 1e6+100;
const int inf = 0x7fffffff;
int n,k;
int fa[maxn];
void init()
{
    for(int i=0;i<=3*n;i++)
        fa[i] = i;
}
int getfa(int x)
{
    if(x==fa[x])
        return x;
    else
        return fa[x] = getfa(fa[x]);
}
void merge(int u,int v)
{
    int t1 = getfa(u);
    int t2 = getfa(v);
    if(t1!=t2)
        fa[t1] = t2;
}
int main(void)
{
    int ans = 0;
    scanf("%d %d",&n,&k);
    init();
    for(int i=0;i<k;i++)
    {
        int t,x,y;
        scanf("%d %d %d",&t,&x,&y);
        if(x<1 || x>n || y<1 || y>n)
        {
            ans++;
            continue;
        }
        int t1 = getfa(x);
        int t2 = getfa(y+n);
        int t3 = getfa(y+2*n);
        if(t==1)
        {
            if(t1==t2 || t1==t3)
                ans++;
            else
            {
                merge(x,y);
                merge(x+n,y+n);
                merge(x+2*n,y+2*n);
            }
        }
        else
        {
            t2 = getfa(y);
            if(t1==t2 || t1==t3)
                ans++;
            else
            {
                merge(x,y+n);
                merge(x+2*n,y);
                merge(x+n,y+2*n);
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}