Poj(1182),种类并查集

#include <stdio.h>

int father[50010];
int rank[50010];

int Find_Set (int x)
{
int tmp;
if(x!=father[x])
{
tmp = father[x];
father[x] = Find_Set(father[x]);        ///一定是先Find_Set，再计算rank,我这里一不小心就WA了，你必须是找到他的父节点的全值，才能计算x的权值.
rank[x] = (rank[x]+rank[tmp])%3;
}
return father[x];
}

int main()
{
int N,M;
scanf("%d%d",&N,&M);
for(int i=1; i<=N; i++)
{
rank[i]  = 0;
father[i] = i;
}

int ans = 0;
for(int i=0; i<M; i++)
{
int flag,x,y;
scanf("%d%d%d",&flag,&x,&y);

if((flag==2&&x==y)||x>N||y>N)
{
ans++;
continue;
}
int fx = Find_Set(x);
int fy = Find_Set(y);
if(flag==1)
{
if(fx==fy)
{
if(rank[x]!=rank[y])
ans++;
}
else
{
father[fy] = fx;
rank[fy] = (rank[x]-rank[y]+3)%3;   ///加上3，也没什么重要的含义咯，会模掉，k-0+3%3
}
}
else
{
if(fx==fy)
{
if(rank[x]!=(rank[y]+1)%3)  ///可以吃，关系只相差1
ans++;
}
else
{
father[fy] = fx;
rank[fy] = (rank[x]-rank[y]+2)%3;   ///合并，+2没什么含义咯，这样理解，就是说，0与0，下一个就是2啦，0吃2,2吃1,1吃0
}
}
}
printf("%d\n",ans);
return 0;
}