Kruskal HDOJ 1863 畅通工程

题目传送门

/*
    此题为：HDOJ 1233 + HDOJ 1232
*/
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;

const int MAX_N = 100 + 10;
int pre[MAX_N];
int tot;
int sum;
struct NODE
{
    int x, y;
    int len;
}node[MAX_N];

int find(int root)
{
    int son, tmp;
    son = root;

    while (root != pre[root])
    {
        root = pre[root];
    }
    while (son != root)
    {
        tmp = pre[son];
        pre[son] = root;
        son = tmp;
    }

    return root;
}

bool cmp(NODE a, NODE b)
{
    return a.len < b.len;
}

int main(void)        //HDOJ 1863 畅通工程
{
    //freopen ("inC.txt", "r", stdin);
    int n, m;        //n路， m村庄

    while (~scanf ("%d%d", &n, &m) && n)
    {
        tot = m - 1;
        for (int i=1; i<=m; ++i)
        {
            pre[i] = i;
        }
        for (int i=1; i<=n; ++i)
        {
            scanf ("%d%d%d", &node[i].x, &node[i].y, &node[i].len);
        }
        sort (node+1, node+1+n, cmp);
        sum = 0;
        for (int i=1; i<=n; ++i)
        {
            int a, b;
            a = find (node[i].x);
            b = find (node[i].y);
            if (a != b)
            {
                pre[a] = b;
                sum += node[i].len;
                --tot;
            }
        }
        if (tot == 0)
            printf ("%d
", sum);
        else
            puts ("?");
    }
}