Kruskal HDOJ 1863 畅通工程

题目传送门

 1 /*
 2     此题为：HDOJ 1233 + HDOJ 1232
 3 */
 4 #include <cstdio>
 5 #include <algorithm>
 6 #include <cstring>
 7 #include <cmath>
 8 using namespace std;
 9
10 const int MAX_N = 100 + 10;
11 int pre[MAX_N];
12 int tot;
13 int sum;
14 struct NODE
15 {
16     int x, y;
17     int len;
18 }node[MAX_N];
19
20 int find(int root)
21 {
22     int son, tmp;
23     son = root;
24
25     while (root != pre[root])
26     {
27         root = pre[root];
28     }
29     while (son != root)
30     {
31         tmp = pre[son];
32         pre[son] = root;
33         son = tmp;
34     }
35
36     return root;
37 }
38
39 bool cmp(NODE a, NODE b)
40 {
41     return a.len < b.len;
42 }
43
44 int main(void)        //HDOJ 1863 畅通工程
45 {
46     //freopen ("inC.txt", "r", stdin);
47     int n, m;        //n路， m村庄
48
49     while (~scanf ("%d%d", &n, &m) && n)
50     {
51         tot = m - 1;
52         for (int i=1; i<=m; ++i)
53         {
54             pre[i] = i;
55         }
56         for (int i=1; i<=n; ++i)
57         {
58             scanf ("%d%d%d", &node[i].x, &node[i].y, &node[i].len);
59         }
60         sort (node+1, node+1+n, cmp);
61         sum = 0;
62         for (int i=1; i<=n; ++i)
63         {
64             int a, b;
65             a = find (node[i].x);
66             b = find (node[i].y);
67             if (a != b)
68             {
69                 pre[a] = b;
70                 sum += node[i].len;
71                 --tot;
72             }
73         }
74         if (tot == 0)
75             printf ("%d\n", sum);
76         else
77             puts ("?");
78     }
79 }