[Ybtoj Chapter 11 Example 1] Busy City [Minimum Spanning Tree]

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Problem-solving ideas

For the minimum spanning tree template question, both prim and kruskal can be used. This question directly tells us the side, and kruskal is more convenient to be greedy by side.

Blog recommendation:

• Minimum Spanning Tree & Prim's Algorithm
• Minimum Spanning Tree & Kruskal
• Jacques Carr

PS: I think it’s the most commonly used.

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Code

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

int n,m,x,y,w,ans,k,fa[310];

struct c{
    
    
	int x,y,w;
}a[310];

bool cmp(c l,c r)
{
    
    
	return l.w<r.w;
}

int find(int x)
{
    
    
	if(x==fa[x])return x;
	else return fa[x]=find(fa[x]);
}

int main(){
    
    
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++)
		scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].w);
	sort(a+1,a+m+1,cmp);
	for(int i=1;i<=n;i++)	
		fa[i]=i;
	printf("%d ",n-1);
	for(int i=1;i<=m;i++)
	{
    
    
		int p=find(a[i].x),q=find(a[i].y);
		if(p!=q)
		{
    
    
			fa[p]=q;
			ans=max(ans,a[i].w);
			k++;
			if(k==n-1)
			{
    
    
				printf("%d",ans);
				return 0;	
			}
		}
	}
}