洛谷 1195 口袋的天空

//Twenty
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<ctime>
#include<queue>
const int maxn=1e5+5;
using namespace std;
typedef long long LL;
int ans,n,m,k,u,v,w,cnt,fa[maxn];

void read(int &ret) {
    int f=1; ret=0; char ch=getchar();
    while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();
    if(ch=='-') f=-1,ch=getchar();
    for(;ch>='0'&&ch<='9';ch=getchar()) ret=ret*10+ch-'0'; ret*=f;
}

struct edge{
	int u,v,w;
	edge(){}
	edge(int u,int v,int w):u(u),v(v),w(w){}
	friend bool operator <(const edge&A,const edge&B) {
	    return A.w<B.w;
	}
}e[maxn];

int find(int x) {
    return x==fa[x]?x:fa[x]=find(fa[x]);
}

void init() {
	read(n); read(m); read(k);
	for(int i=1;i<=m;i++) {
	    read(u); read(v); read(w);
	    e[++cnt]=edge(u,v,w);
	}
	sort(e+1,e+cnt+1);
	for(int i=1;i<=n;i++) fa[i]=i;
	for(int i=1;i<=cnt;i++) {
	    u=e[i].u; v=e[i].v; w=e[i].w;
	    int x=find(u),y=find(v);
	    if(x!=y) {
		    ans+=w;
		    fa[x]=y;
		    n--;
		    if(n==k) break;
		} 
	}
	printf("%d
",ans);
}

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