【模板】最小生成树

题目链接

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一、kruskal

#include<cstdio>
#include<algorithm> 
using namespace std;
const int NN = 5e3+8, MM = 2e5+8;
int N, M;
int ans,cnt;
int fa[NN];
struct Edge{
	int from,to,len;
	#define f(x) edge[x].from
	#define t(x) edge[x].to
	#define len(x) edge[x].len
	bool operator < (const Edge &x) const{
		return len < x.len;
	} 
}edge[MM];
int find(int x){
	if(x == fa[x]) return x;
	return fa[x] = find(fa[x]);
}
void merge(int x,int y){//把y连在x上 
	fa[find(x)] = fa[find(y)]; 
}
void add_edge(int i){
	merge(f(i),t(i));
	ans += len(i);
}
int main(){
	scanf("%d%d",&N,&M);
	for(int i = 1; i <= N; i++) fa[i] = i;
	for(int i = 1; i <= M; i++) scanf("%d%d%d",&f(i),&t(i),&len(i));
	sort(edge + 1, edge + 1 + M);
	for(int i = 1; i <= M; i++){
		int X = find(f(i)),Y = find(t(i));
		if(X != Y)
			add_edge(i);
	}
	for(int i = 1; i <= N; i++)
		if(fa[i] == i) ++cnt;
	if(cnt == 1) printf("%d",ans);
	else printf("orz");
}