用最短路的方法找最长路。。。哎黑心商家没有好结果啊
ac:
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 1000005;
struct node{
int from,to,dis;
}edge[maxn];
int n,fa[maxn],m,ans,tree=0;
bool cmp(node a,node b)
{
return a.dis>b.dis;
}
int find(int x)
{
if(fa[x]==x)
return x;
return fa[x]=find(fa[x]);
}
void mix(int x,int y)
{
x=find(x),y=find(y);
if(x!=y) fa[y]=x;
}
int kruskal()
{
sort(edge,edge+m,cmp);
for(int i=0;i<=n;i++)
{
fa[i]=i; //初始化
}
ans=0;
for(int i=0;i<m;i++)
{
if(find(edge[i].from)!=find(edge[i].to))
{
mix(edge[i].from,edge[i].to);
ans+=edge[i].dis;
tree++;
}
}
return ans;
}
int main()
{
scanf("%d %d",&n,&m);
for(int i=0;i<m;i++)
{
scanf("%d%d%d",&edge[i].from,&edge[i].to,&edge[i].dis);
}
kruskal();
if(tree<n-1)
printf("-1");
else
printf("%d\n",kruskal());
}