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| #include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#define INF 1<<30
#define maxn 1010
using namespace std;
int G[maxn+1][maxn+1];
int intree[maxn];
int minweight[maxn];
int sumweight;
int flag=0;
void chushihua()
{
memset(intree,0,sizeof(intree));
memset(minweight,0,sizeof(minweight));
flag=0;
for(int i=0;i<maxn;i++)
{
for(int j=0;j<=maxn;j++)
{
G[i][j]=INF;
}
}
sumweight=0;
}
void prime(int n)
{
int node,Minweight;
for(int i=1;i<=n;i++)
minweight[i]=G[1][i];
intree[1]=1;
for(int i=2;i<=n;i++)
{
Minweight=INF;
for(int j=1;j<=n;j++)
{
if(minweight[j]<Minweight&&!intree[j])
{
Minweight=minweight[j];
node=j;
}
}
intree[node]=1;
sumweight+=Minweight;
for(int j=1;j<=n;j++)
{
if(!intree[j]&&minweight[j]>G[node][j])
{
minweight[j]=G[node][j];
}
}
}
}
int main()
{
int n,m;
while(scanf("%d%d",&n,&m)!=EOF)
{
int a1,a2,v;
chushihua();
for(int i=1;i<=m;i++)
{
scanf("%d%d%d",&a1,&a2,&v);
G[a1][a2]=-v;
G[a2][a1]=-v;
}
prime(n);
for(int i=1;i<=n;i++)
{
if(intree[i]==0)
{flag=1;
break;}
}
if(flag)
printf("-1\n");
else
printf("%d\n",-sumweight);
}
return 0;
}
|
