USACO 3.1 Agri-Net(prim模版)

虽然好久没敲过了prim，迅速秒掉。

 1 /*

 2   ID: cuizhe

 3   LANG: C++

 4   TASK: agrinet

 5 */

 6 #include <iostream>

 7 #include <cstdio>

 8 #include <cstring>

 9 #include <cmath>

10 #include <algorithm>

11 using namespace std;

12 #define N 100000000

13 int p[101][101],low[101],o[101];

14 int main()

15 {

16     int i,j,k,n,t,ans;

17     freopen("agrinet.in","r",stdin);

18     freopen("agrinet.out","w",stdout);

19     scanf("%d",&n);

20     for(i = 1;i <= n;i ++)

21     {

22         for(j = 1;j <= n;j ++)

23         scanf("%d",&p[i][j]);

24     }

25     o[1] = 1;

26     for(i = 1;i <= n;i ++)

27     low[i] = p[1][i];

28     ans = 0;

29     for(i = 1;i <= n-1;i ++)

30     {

31         t = N;

32         for(j = 1;j <= n;j ++)

33         {

34             if(!o[j]&&t > low[j])

35             {

36                 t = low[j];

37                 k = j;

38             }

39         }

40         if(t == N) break;

41         o[k] = 1;

42         ans += t;

43         for(j = 1;j <= n;j ++)

44         {

45             if(low[j] > p[k][j]&&!o[j])

46             low[j] = p[k][j];

47         }

48     }

49     printf("%d\n",ans);

50     return 0;

51 }