codevs 1704 [NOI2001] 食物链 并查集

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int MAXN=2000001;
int fa[MAXN];
int n,tot,m;

int find(int x)
{
int r=x,t;
while(r!=fa[r]) r=fa[r];
while(x!=r) t=fa[x],fa[x]=r,x=t;
return r;
}

void merge(int x,int y)
{
fa[find(x)]=find(y);
return;
}

void solve()
{
scanf("%d%d",&n,&m);
for(int i=1;i<=n*3;i++) fa[i]=i;

for(int i=1;i<=m;i++)
{
int opt,x,y;
scanf("%d%d%d",&opt,&x,&y);
if(x>n || y>n) {tot++;continue;}
if(opt==1)
{
if(find(x+n)==find(y) || find(x+2*n)==find(y)) tot++;
else
{
merge(x,y);
merge(x+n,y+n);
merge(x+2*n,y+2*n);
}
}
else
{
if(find(x+n)==find(y) || find(x)==find(y)) tot++;
else
{
merge(x+2*n,y);
merge(x,y+n);
merge(x+n,y+2*n);
}
}
}
cout<<tot;
return;
}

int main()
{
solve();
return 0;
}