最小生成树-prim算法模板

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define inf 10000000
#define maxn 21
int m,n;
int edge[maxn][maxn],lowcost[maxn],nearvex[maxn];
void prim(int u0)
{
int i,j;
int sumweight=0;
for(i=1; i<=n; i++)
{
lowcost[i]=edge[u0][i];
nearvex[i]=u0;
}
nearvex[u0]=-1;
for(i=1; i<n; i++)
{
int min=inf;
int v=-1;
for(j=1; j<=n; j++)
{
if(nearvex[j]!=-1 && lowcost[j]<min)
{
v=j;
min=lowcost[j];
}
}
if(v!=-1)
{
cout<<nearvex[v]<<" "<<v<<" "<<lowcost[v]<<endl;
nearvex[v]=-1;
sumweight+=lowcost[v];
for(j=1; j<=n; j++)
{
if(nearvex[j]!=-1 && edge[v][j]<lowcost[j])
{
lowcost[j]=edge[v][j];
nearvex[j]=v;
}
}
}
}
cout<<"weight of mst is "<<sumweight<<endl;
}
int main()
{
ios::sync_with_stdio(false);
freopen("1.txt","r",stdin);
int i,j,w,u,v;
cin>>n>>m;
memset(edge,0,sizeof(edge));
for(i=1; i<=m; i++)
{
cin>>u>>v>>w;
edge[u][v]=edge[v][u]=w;
}
for(i=1; i<=n; i++)
{
for(j=1; j<=n; j++)
{
if(i==j)
edge[i][j]=0;
else if(edge[i][j]==0)
edge[i][j]=inf;
}
}
prim(1);
return 0;
}

/*
7 9
1 2 28
1 6 10
2 3 16
2 7 14
3 4 12
4 5 22
4 7 18
5 6 25
5 7 24

*/