POJ1679 次小生成树

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 using namespace std;
 5 const int maxn = 105;
 6 struct node
 7 {
 8     int u,v,w;
 9 }e[maxn*maxn];
10 int fa[maxn],MST[maxn];
11 bool cmp(node a,node b)
12 {
13     return a.w<b.w;
14 }
15 int findd(int x)
16 {
17     int rt = x;
18     while(rt!=fa[rt])rt = fa[rt];
19     while(x!=rt)
20     {
21         int t = fa[x];
22         fa[x] = rt;
23         x = t;
24     }
25     return rt;
26 }
27 int main()
28 {
29     int T;scanf("%d",&T);
30     while(T--)
31     {
32         int n,m;scanf("%d%d",&n,&m);
33         for(int i = 1;i<=m;++i)
34             scanf("%d%d%d",&e[i].u,&e[i].v,&e[i].w);
35         sort(e+1,e+1+m,cmp);
36         for(int i = 1;i<=n;++i)fa[i] = i;
37         int cnt = 0,w_MST = 0;
38         for(int i = 1;i<=m;++i)
39         {
40             int fx = findd(e[i].u),fy = findd(e[i].v);
41             if(fx==fy)continue;
42             fa[fx] = fy;
43             MST[++cnt] = i;
44             w_MST+=e[i].w;
45         }
46         int flag = 1;
47         for(int i = 1;i<=cnt;++i)
48         {
49             for(int j = 1;j<=n;++j)fa[j] = j;
50             int sum = 0;
51             for(int j = 1;j<=m;++j)if(j!=MST[i])
52             {
53                 int fx = findd(e[j].u),fy = findd(e[j].v);
54                 if(fx==fy)continue;
55                 fa[fx] = fy;
56                 sum+=e[j].w;
57             }
58             int ok = 1;
59             for(int j = 2;j<=n;++j)if(fa[j]!=fa[1])//error
60             {
61                 ok = 0;break;
62             }
63 
64             if(ok && sum==w_MST){flag = 0;break;}
65         }
66         if(flag)printf("%d\n",w_MST);
67         else printf("Not Unique!\n");
68     }
69     return 0;
70 }