POJ 1679 The Unique MST

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 const int VM=120;
 7 const int EM=10010;
 8 struct Edge{
 9     int u,v,cap;
10     bool operator < (const Edge& a)const {
11         return cap<a.cap;
12     }
13 }edge[EM<<1];
14 int n,m,flag,ans,father[VM];
15 void makeSet(){
16     for(int i=1;i<=n;i++)
17         father[i]=i;
18 }
19 int findSet(int x){
20     if(x==father[x]) return x;
21     else return  father[x]=findSet(father[x]);
22 }
23 void Kruskal(){
24     makeSet();
25     sort(edge,edge+m);
26     int path[EM],cnt=0;
27     ans=0;
28     for(int i=0;i<m;i++){
29         int u=findSet(edge[i].u);
30         int v=findSet(edge[i].v);
31         if(u!=v){
32             father[v]=u; ans+=edge[i].cap;
33             path[cnt++]=i;      //记录路径
34         }
35     }
36     for(int k=0;k<cnt;k++){     //枚举去掉每一条边
37         makeSet();
38         int sum=0,j=0;
39         for(int i=0;i<m;i++){
40             if(i==path[k]) continue;
41             int u=findSet(edge[i].u),v=findSet(edge[i].v);
42             if(u!=v){
43                 father[v]=u;
44                 sum+=edge[i].cap;
45                 j++;
46             }
47         }
48         if(j==n-1 && sum==ans){     //判断是否能构成树 且 是否与最小生成树相等
49             flag=0;return ;
50         }
51     }
52 }
53 int main(){
54     int T;
55     scanf("%d",&T);
56     while(T--){
57         scanf("%d%d",&n,&m);
58         for(int i=0;i<m;i++)
59             scanf("%d%d%d",&edge[i].u,&edge[i].v,&edge[i].cap);
60         flag=1;
61         Kruskal();
62         if(flag) printf("%d\n",ans);
63         else printf("Not Unique!\n");
64     }
65     return 0;
66 }