题意：求最小生成树跟次小生成树
AC代码
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
using namespace std;
const int maxn=1010;
const int inf=0x3f3f3f3f;
int Map[maxn][maxn],dis[maxn],pre[maxn],maxx[maxn][maxn];
bool vis[maxn],used[maxn][maxn];
int n,m;
vector<int> p;
int prim(int cur)
{memset(vis,false,sizeof(vis));memset(used,false,sizeof(used));// vis[cur]=true;for(int i=1;i<=n;i++){dis[i]=inf;}dis[1]=0;pre[1]=1;p.clear();int sum=0;for(int i=1;i<=n;i++){int minn=inf,u;for(int j=1;j<=n;j++){if(!vis[j]&&minn>dis[j]){minn=dis[j];u=j;}}sum+=Map[pre[u]][u];vis[u]=true;used[u][pre[u]]=used[pre[u]][u]=true;int size1=p.size();for(int j=0;j<size1;j++){maxx[p[j]][u]=maxx[u][p[j]]=max(maxx[p[j]][pre[u]],Map[pre[u]][u]);}p.push_back(u);for(int j=1;j<=n;j++){if(!vis[j]&&dis[j]>Map[u][j]){dis[j]=Map[u][j];pre[j]=u;}}}return sum;
}
int smst()
{int sum=prim(1);int ans=inf;for(int i=1;i<=n;i++){for(int j=i+1;j<=n;j++){if(!used[i][j]&&Map[i][j]!=inf){ans=min(ans,sum+Map[i][j]-maxx[i][j]);}}}return ans;
}
void init()
{for(int i=1;i<=n;i++){for(int j=1;j<=n;j++){if(i==j) Map[i][j]=0;else Map[i][j]=inf;}}
}
int main()
{std::ios::sync_with_stdio(false);int t;cin>>t;while(t--){cin>>n>>m;init();for(int i=1;i<=m;i++){int a,b,c;cin>>a>>b>>c;Map[a][b]=min(Map[a][b],c);Map[b][a]=min(Map[b][a],c);}int ans1=prim(1);int ans2=smst();cout<<ans1<<" "<<ans2<<endl;}return 0;
}