最小生成树板板

prim朴朴素素 

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
int n,m,minn,k,ans;
const int INF=0x7fffffff/2;
int f[1000000],mn[1000000];
int a[5001][5001];
int x,y,w;
int main() {
	int i,j;
	scanf("%d%d",&n,&m);
	memset(a,0x7f,sizeof(a));
	for(i=1; i<=m; i++) {
		scanf("%d%d%d",&x,&y,&w);
		a[y][x]=a[x][y]=min(a[y][x],w);
	}
	memset(mn,0x7f,sizeof(mn));
	mn[1]=0;
	for(i=1; i<=n; i++) {
		minn=INF;
		for(j=1; j<=n; j++)
			if(f[j]==0&&mn[j]<minn) {
				minn=mn[j];
				k=j;
			}
		f[k]=1;
		ans+=minn;
		for(j=1; j<=n; j++)
			if(f[j]==0&&mn[j]>a[k][j]) mn[j]=a[k][j];
	}
	cout<<ans<<endl;
	return 0;
}

prim结构体

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#define INF 0x7f7ff; 
using namespace std;
int n,m,head[5010],x,y,z,cnt,ans;
int mn[5010],f[5010];
struct deliver{
	int to;
	int nexty;
	int w;
}edge[400010];
void add(int u,int v,int c) {
	cnt++;
	edge[cnt].nexty=head[u];
	edge[cnt].to=v;
	edge[cnt].w=c;
	head[u]=cnt;
}
int main() {
	int i,j,k;
	cin>>n>>m;
	for(i=1;i<=m;i++) {
		scanf("%d%d%d",&x,&y,&z);
		add(x,y,z);
		add(y,x,z);
	}
	memset(mn,0x7f,sizeof(mn));
	mn[1]=0;
	for(i=1;i<=n;i++) {
		int minn=INF;
		for(j=1;j<=n;j++) {
			if(f[j]==0&&mn[j]<minn) {
				k=j;
				minn=mn[j];
			}
		}
		f[k]=1;
		ans+=mn[k];
		for(j=head[k];j;j=edge[j].nexty) {
			int r=edge[j].to;
			if(f[r]==0&&mn[r]>edge[j].w) mn[r]=edge[j].w;
		}
	}
	cout<<ans<<endl;
	return 0;
}

krus

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
int n,m,ans,cnt;
int f[200009];
struct deliver {
	int z;
	int x;
	int y;
}b[200009];
int find(int k) {
	if(f[k]==k) return k;
	f[k]=find(f[k]);
	return f[k];
}
int cmp(deliver p,deliver q) {
	return p.z<q.z;
}
void krs() {
	int i;
	for(i=1;i<=m;i++) 
		if(find(b[i].x)!=find(b[i].y)) {
			ans+=b[i].z;
		    f[find(b[i].x)]=find(b[i].y);
		    cnt++;
		    if(cnt==n-1) break;
	    }
}
int main() {
	int i,j,k;
	scanf("%d%d",&n,&m);
	for(i=1;i<=n;i++) 
	   f[i]=i;
	for(i=1;i<=m;i++) {
		scanf("%d%d%d",&b[i].x,&b[i].y,&b[i].z);
		//f[find(b[i].x)]=find(b[i].y);多余 
	}
	sort(b,b+m+1,cmp);
	krs();
	cout<<ans;
	return 0;
}