hdu 1863 

 1 //裸的kruskal，如果不会的多看下并查集吧，不多说了
 2 #include<stdio.h>
 3 #include<string.h>
 4 #include<algorithm>
 5 using namespace std;
 6 #define maxn 100
 7 int fa[maxn],rank[maxn];
 8 struct node
 9 {
10     int st,nd,ln;
11 }edge[maxn*maxn];
12 int cmp(node a,node b)
13 {
14     return a.ln<b.ln;
15 }
16 void init()
17 {
18     int i;
19     for(i=0;i<maxn;i++)
20     {
21         rank[i]=1;
22         fa[i]=i;
23     }
24 }
25 int findfather(int x)
26 {
27     if(x!=fa[x])
28         fa[x]=findfather(fa[x]);
29     return fa[x];
30 }
31 void kruskal(int n,int m)
32 {
33     int ans,num,i,x,y;
34     ans=num=0;
35     sort(edge+1,edge+1+n,cmp);
36     for(i=1;i<=n;i++)
37     {
38         x=findfather(edge[i].st);
39         y=findfather(edge[i].nd);
40         if(x!=y)
41         {
42             ans+=edge[i].ln;
43             if(rank[x]>rank[y])
44             {
45                 fa[y]=x;
46                 rank[x]+=rank[y];
47             }
48             else
49             {
50                 fa[x]=y;
51                 rank[y]+=rank[x];
52             }
53             if(++num==m-1)
54                 break;
55         }
56     }
57     if(num==m-1)
58         printf("%d\n",ans);
59     else
60         printf("?\n");
61 }
62 int main()
63 {
64     int n,m,i;
65     while(scanf("%d",&n)!=EOF)
66     {
67         init();
68         scanf("%d",&m);
69         if(n==0)
70             break;
71         for(i=1;i<=n;i++)
72         {
73             scanf("%d%d%d",&edge[i].st,&edge[i].nd,&edge[i].ln);
74         }
75         if(n<m-1)
76         {
77             printf("?\n");
78             continue;
79         }
80         kruskal(n,m);
81     }
82     return 0;
83 }

 

posted @ 2012-08-08 17:24  M_cag  阅读(356)  评论(0)    收藏  举报