poj1182(并查集）

把两个节点的关系转换为对根节点的关系的比较

#include <stdio.h>
int father[50001] ,r[50001];
void init(int n)
{
    int i;
    for(i = 1 ; i <= n ; i++)
    {
        father[i] = i;
        r[i] = 0;
    }
}
int find(int x)
{
    if(x == father[x])
    return father[x];
    else
    {
         int pre = father[x];
        father[x] = find(father[x]);
        r[x] = (r[x]+r[pre])%3;
    }
    return father[x];
}
void union1(int x, int y,int d)
{
    father[x] = y;
    r[x] = d%3;
}
int main()
{
    int k,d, x, y, i, j,n,num = 0;
    scanf("%d%d", &n,  &k);
    init(n);
    while(k--)
    {
        scanf("%d%d%d", &d,&x, &y);
        if(x>n||y>n||(d == 2&&x == y))
        num++;
        else
        {
            int pa = find(x);
            int pb = find(y);
            if(pa == pb)
            {
                if(d ==1)
                {
                    if(r[x] != r[y])
                    num++;
                }
                else
                {
                    if(r[x]!=(r[y]+1)%3)
                     num++;
                }
            }
            else
            union1(pa,pb,r[y]-r[x]+d+2);
        }
    }
    printf("%d\n",num);
    return 0;
}