洛谷 P1546 最短网络 Agri-Net（最小生成树）

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 int cnt, f[1005];
 7 
 8 int k, h;
 9 struct node{
10     int x, y, l;
11 } a[110005];
12 
13 inline int cmp(node i, node j){
14     return i.l < j.l;
15 }
16 
17 inline int find(int x){
18     if(f[x] != x)
19         f[x] = find(f[x]);
20     return f[x];
21 }
22 
23 int main(){
24     int n;
25     int z;
26     scanf("%d", &n);
27     for(int i = 1; i <= n; i++){
28         for(int j = 1; j <= n; j++){
29             scanf("%d", &z);
30             if(j > i){ //只读取上面一半有用的数据 
31                 a[++cnt].x = i;
32                 a[cnt].y = j;
33                 a[cnt].l = z;
34             }
35         }
36     }
37     for(int i = 1; i <= n; i++)
38         f[i] = i;
39     sort(a+1, a+cnt+1, cmp);
40     for(int i = 1; i <= cnt; i++){
41         int r1 = find(a[i].x);
42         int r2 = find(a[i].y);
43         if(r1 != r2){
44             f[r1] = r2;
45             h += a[i].l;
46             k++;
47         }
48         if(k == n-1) break;//跳出 
49     }
50     printf("%d", h);
51     return 0;
52 }