2 1
0 1 10

4 0

10

impossible

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<cmath>
using namespace std;

int n,m;
int pre[1010];
struct node{
       int u;
       int v;
       int w;
};
node sb[10010];

bool cmp(node a,node b)
{
     return a.w<b.w;
}

int find(int x)
{
    if(pre[x]==x)
    return x;
    return pre[x]=find(pre[x]);
    }

bool join(int x,int y)
{
     int f1,f2;
     f1=find(x);
     f2=find(y);
     if(f1==f2)
     return false;
     if(f1!=f2)
     pre[f1]=f2;
     return true;
}

int main()
{
    int sum;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
           sum=0;
          for(int i=0;i<n;i++)
          pre[i]=i;
          for(int i=0;i<m;i++)
          scanf("%d%d%d",&sb[i].u,&sb[i].v,&sb[i].w);
          sort(sb,sb+m,cmp);
          for(int i=0;i<m;i++)
          {
             if(join(sb[i].u,sb[i].v))
             sum+=sb[i].w;
          }
          int cnt=0;
          for(int i=0;i<n;i++)
          {
                  if(pre[i]==i)
                cnt++;
          }
          if(cnt>1)
          printf("impossible\n\n");
          else
          printf("%d\n\n",sum);
    }
    return 0;
}

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
const int  INF= 0x3f3f3f3f;
const int maxb=1010;
int  map[maxb][maxb];
int vis[maxb];
int n,m,sum;
int a,b,c;

void prime()
{
    int i,j,k,dis[maxb];
    int min;
    memset(vis,0,sizeof(vis));
    int ans=1;
    vis[0]=1;
    for(i=0;i<n;i++)
        dis[i]=map[0][i];
    for(i=0;i<n;i++)
    {
        min=INF;
        for(j=0;j<n;j++)
            if(!vis[j]&&min>dis[j])
            min=dis[k=j];
        if(min==INF)
        {
            if(ans==n)
            printf("%d\n",sum);
            else
            puts("impossible");
            break;
        }
        sum+=min;
        vis[k]=1;
        ans++;
        for(j=0;j<n;j++)
        if(!vis[j]&&dis[j]>map[k][j])
        dis[j]=map[k][j];
    }
}

int main()
{
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(map,INF,sizeof(map));
        sum=0;
        while(m--)
        {
            scanf("%d%d%d",&a,&b,&c);
            if(map[a][b]>c)
            map[a][b]=map[b][a]=c;
        }
        //getchar(); 
        prime();
        //getchar(); 
        puts("");
    }
    return 0;
}