POJ-1258 Agri-Net(kruskal最小生成树)

 1 #include <cstdio>
 2 #include <cmath>
 3 #include <cstdlib>
 4 #include <cstring>
 5 #include <queue>
 6 #include <stack>
 7 #include <vector>
 8 #include <iostream>
 9 #include "algorithm"
10 using namespace std;
11 typedef long long LL;
12 const int MAX=105;
13 int n,m;
14 int a[MAX][MAX],fa[MAX*MAX];
15 struct Edge{
16     int u,v;
17     int val;
18     bool operator <(const Edge &xx) const {
19         return val<xx.val;
20     }
21 }edge[MAX*MAX];
22 int getfather(int x){
23     if (fa[x]==x) return x;
24     return fa[x]=getfather(fa[x]);
25 }
26 void init(){
27     int i,j;
28     for (i=1;i<=n;i++){
29         for (j=1;j<=n;j++){
30             scanf("%d",&a[i][j]);
31         }
32     }
33     m=0;
34     for (i=1;i<=n;i++){
35         for (j=i+1;j<=n;j++){
36             edge[++m].u=i;
37             edge[m].v=j;
38             edge[m].val=a[i][j];
39         }
40     }
41     for (i=1;i<=n;i++)
42         fa[i]=i;
43     sort(edge+1,edge+m+1);
44 }
45 int main(){
46     freopen ("net.in","r",stdin);
47     freopen ("net.out","w",stdout);
48     int i,j,ans;
49     while (~scanf("%d",&n)){
50         init();ans=0;
51         int tx,ty;
52         for (i=1;i<=m;i++){
53             tx=getfather(edge[i].u);
54             ty=getfather(edge[i].v);
55             if (tx!=ty){
56                 ans+=edge[i].val;
57                 fa[tx]=ty;
58             }
59         }
60         printf("%d\n",ans);
61     }
62     return 0;
63 }