poj 1679 The Unique MST (次小生成树(sec_mst)【kruskal】)

 1 #include <map>
 2 #include <queue>
 3 #include <cmath>
 4 #include <vector>
 5 #include <string>
 6 #include <cstdio>
 7 #include <cstring>
 8 #include <climits>
 9 #include <iostream>
10 #include <algorithm>
11 #define INF 0x3f3f3f3f
12 using namespace std;
13 const int my_max_edge = 10010, my_max_node = 110;
14 
15 int t, n, m, my_book_edge[my_max_edge], my_pre[my_max_node], my_first;
16 
17 struct edge
18 {
19     int a, b, val;
20 }P[my_max_edge];
21 
22 bool cmp(edge a, edge b)
23 {
24     return a.val < b.val;
25 }
26 
27 int my_find(int x)
28 {
29     int n = x;
30     while (n != my_pre[n])
31         n = my_pre[n];
32     int i = x, j;
33     while (n != my_pre[i])
34     {
35         j = my_pre[i];
36         my_pre[i] = n;
37         i = j;
38     }
39     return n;
40 }
41 
42 int my_kruskal(int my_flag)
43 {
44     int my_ans = 0;
45     for (int i = 1; i <= n; ++ i)
46         my_pre[i] = i;
47 
48     for (int i = 0; i < m; ++ i)
49     {
50         int n1 = my_find(P[i].a), n2 = my_find(P[i].b);
51         if (n1 == n2 || my_flag == i) continue;
52         my_pre[n1] = n2;
53         if (my_first)my_book_edge[i] = 1;
54         my_ans += P[i].val;
55     }
56 
57     int temp = my_find(1);
58     for (int i = 2; i <= n; ++ i)
59         if (temp != my_find(i))
60             return -1;
61     return my_ans;
62 }
63 
64 int main()
65 {
66     scanf("%d", &t);
67     while (t --)
68     {
69         scanf("%d%d", &n, &m);
70         for (int i = 0; i < m; ++ i)
71             scanf("%d%d%d", &P[i].a, &P[i].b, &P[i].val);
72         sort(P, P + m, cmp);
73         memset(my_book_edge, 0, sizeof(my_book_edge));
74 
75         my_first = 1;
76         int mst = my_kruskal(-1), flag = 1;
77         if (mst == -1)
78         {
79             printf("0\n");
80             continue;
81         }
82         my_first = 0;
83         for (int i = 0; i < m; ++ i)
84         {
85             if (my_book_edge[i])
86             {;
87                 if (mst == my_kruskal(i))
88                 {
89                     printf("Not Unique!\n");
90                     flag = 0;
91                     break;
92                 }
93             }
94         }
95         if (flag) printf("%d\n", mst);
96     }
97     return 0;
98 }