HDU 2473 Junk-Mail Filter 删点并查集

Posted 2020-09-27 wzjhoutai

删点并查集，就是用一个新的点标取代之前的点标就可以。

。 y一下就能够了

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <vector>
#include <map>
#include <queue>
#include <math.h>
#include <string>
#include <set>
using namespace std;
#define mod 1000000007
#define ll int
#define N 100101
ll r[1100010], f[1100010], a[N], top;
ll n, m;
ll find(ll x){return x==f[x]?x:f[x] = find(f[x]);}
void Union(ll x, ll y){
    ll fx = find(x), fy = find(y);
    if(fx==fy)  return;
    if(r[fx]>r[fy])  swap(fx,fy);
    f[fx] = fy;
    r[fy] += r[fx];
}
void Del(ll x){
	find(a[x]);
	a[x] = top;
	r[top] = 1;
	f[top] = top;
	top++;
}
void init(){
    for(ll i = 0; i < n; i++)
        f[i] = a[i] = i, r[i] = 1;
	top = n;
}
set<int>s;
int main(){
	int i, j, u, v, Cas = 1;
	while(scanf("%d %d",&n,&m), n+m){
		init();
		while(m--)
		{
			char c[10]; scanf("%s %d",c,&u);
			if(c[0]==‘M‘)
			{
				scanf("%d",&v);
				Union(a[u], a[v]);
			}
			else Del(u);
		}
		s.clear();
		for(i = 0; i < n; i++) 
		for(i = 0; i < n; i++)
			s.insert(find(a[i]));
		printf("Case #%d: %d\n", Cas++, s.size());
	}
	return 0;
}