POJ 2421 Constructing Roads

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<algorithm>
 5 using namespace std;
 6 int n,m,x,tot,y,fa[1005];
 7 #define maxm 10010
 8 struct node{
 9     int from,to,value; 
10     bool operator < (const node& a) const {
11         return value<a.value;
12     }
13 }edge[maxm*4];
14 void add_edge(int u,int v,int w){
15     edge[++tot].from=u;edge[tot].to=v;edge[tot].value=w;
16 }
17 int find(int x){
18     if(x==fa[x]) return x;
19     else return fa[x]=find(fa[x]);
20 }
21 int main()
22 {
23     scanf("%d",&n);
24     for(int i=1;i<=n;i++)
25         for(int j=1;j<=n;j++){
26             scanf("%d",&x);
27              add_edge(i,j,x);
28         }
29     scanf("%d",&m);
30     for(int i=1;i<=m;i++){
31         scanf("%d%d",&x,&y);
32         add_edge(x,y,0);add_edge(y,x,0);
33     }
34     sort(edge+1,edge+tot+1);
35     int t=0,ans=0;
36     for(int i=1;i<=n+5;i++) fa[i]=i;
37     for(int k=1;k<=tot;k++){
38         int x=edge[k].from,y=edge[k].to;
39         int rx=find(x),ry=find(y);
40         if(rx!=ry){
41             ans+=edge[k].value;
42             fa[rx]=ry;
43             t++;
44         }
45         if(t== n-1 ) break;
46     }
47     printf("%d\n",ans);
48     return 0;
49 }