HDOJ 1863

#include<stdio.h>
#include<string.h>
int father[105],depth[105];
int dist[105],map[101][101];
int vis[105],n;
void init_B()
{
    int i;
    for(i = 1;i <= n;i ++)
    {
        father[i] = i;
        depth[i] = 0;
    }
}

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

void unit(int x,int y)
{
    x = find(x);
    y = find(y);
    if(x == y)
        return ;
    if(depth[x] < depth[y])
        father[x] = y;
    else
    {
        if(depth[x] > depth[y])
            father[y] = x;
        else
        {
            father[x] = y;
            depth[y]++;
        }
    }
}

void init()
{
    int i;
    memset(vis,0,sizeof(vis));
    for(i = 1;i <= n;i ++)
        dist[i] = map[1][i];
}

int main()
{
    int m,i,j,k,a,b;
    int min,cnt,cost,sum;
    while(~scanf("%d%d",&m,&n) && m)
    {
        init_B();
        sum = cnt = 0;
        for(i = 1;i <= n;i ++)
        {
            for(j = 1;j <= n;j ++)
            {
                if(i != j)
                {
                    map[i][j] = 1 << 30;
                }
            }
        }
        while(m--)
        {
            scanf("%d%d%d",&a,&b,&cost);
            map[a][b] = map[b][a] = cost;
            unit(a,b);
        }
        init();
        for(i = 1;i <= n;i ++)
        {
            if(i == find(i))
                cnt++;
            if(cnt == 2)
                break ;
        }
        if(cnt == 2)
        {
            printf("?\n");
            continue ;
        }
        for(i = 0;i < n;i ++)
        {
            min = 1 << 30;
            for(j = 1;j <= n;j ++)
            {
                if(!vis[j] && min > dist[j])
                {
                    min = dist[j];
                    k = j;
                }
            }
            vis[k] = 1;
            if(min != 1 << 30)
                sum += min;
            for(j = 1;j <= n;j ++)
            {
                if(!vis[j] && dist[j] > map[k][j])
                    dist[j] = map[k][j];
            }
        }
        printf("%d\n",sum);
    }
    return 0;
}