POJ-1258 Agri-Net(最小生成树)

 1 #include <cstdio>
 2 #include <cmath>
 3 #include <cstring>
 4 #include <cstdlib>
 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 f[MAX][MAX];
15 int ans;
16 struct Edge{
17     int u,v;
18     int w;
19 }edge[MAX*MAX];
20 int fa[MAX*MAX];
21 int getfather(int x){
22     if (fa[x]==x)
23      return x;
24     return fa[x]=getfather(fa[x]);
25 }
26 bool cmp(Edge x,Edge y){
27     return x.w<y.w;
28 }
29 void init(){
30     int i,j;
31     for (i=1;i<=n;i++)
32      for (j=1;j<=n;j++)
33       scanf("%d",&f[i][j]);
34     m=0;
35     for (i=1;i<=n;i++)
36      for (j=i+1;j<=n;j++)
37      {m++;
38       edge[m].u=i;
39       edge[m].v=j;
40       edge[m].w=f[i][j];
41      }
42     for (i=1;i<=m;i++)
43      fa[i]=i;
44     sort(edge+1,edge+m+1,cmp);
45 }
46 int main(){
47     freopen ("net.in","r",stdin);
48     freopen ("net.out","w",stdout);
49     while (scanf("%d\n",&n)!=EOF){
50     init();int i,j;
51     ans=0;
52     int tx,ty;
53     for (i=1;i<=m;i++)
54     {tx=getfather(edge[i].u);
55      ty=getfather(edge[i].v);
56      if (tx!=ty)
57      {fa[tx]=ty;
58       ans+=edge[i].w;
59      }
60     }
61     printf("%d\n",ans);}
62     return 0;
63 }