HDOJ 1598 Kruscal

贪心思想的Kruscal：先对边排序，再从第一条边开始，一旦start point 和 end poiont 连上，就break

 1 #include <stdio.h>

 2 #include <iostream>

 3 #include <algorithm>

 4 const int N = 1010;

 5 const int inf = 1000000;

 6 using namespace std;

 7 

 8 struct Road{

 9     int st,ed,pd; //起点，终点、速度

10 }road[N];

11 int cmp(const Road &p,const Road &q){

12     return p.pd<q.pd;

13 }

14 int root[N];

15 int n,m;

16 void init(){

17     for(int i = 1; i <= n; i++){

18         root[i] = -1;

19     }

20 }

21 int Find(int x){

22     int s = x;

23     while(root[s] >= 0){      //一直查到parent[s]为负数（此时s为根结点)为止

24         s = root[s];

25     }

26     while(s != x){              //路径压缩，优化，便于后续的查找操作加速

27         int temp = root[x];

28         root[x] = s;

29         x=temp;

30     }

31     return s;

32 }

33 void Union(int R1,int R2){

34     int r1 = Find(R1);

35     int r2 = Find(R2);

36     if(r1 != r2){

37         root[r2] = r1;

38     }

39 }

40 int main(){

41     int _case;

42     while(scanf("%d%d",&n,&m)!=EOF){

43         for(int i = 1; i <= m; i++){\

44             scanf("%d%d%d",&road[i].st,&road[i].ed,&road[i].pd);

45         }

46         sort(road+1, road+1 + m, cmp);  //calculating form 1

47         scanf("%d",&_case);

48         while(_case--){

49             int st,ed;

50             int min = inf;

51             scanf("%d%d",&st,&ed);

52             for(int i = 1; i <= m; i++){

53                 init();

54                 for(int j = i; j <= m; j++){

55                     Union(road[j].st, road[j].ed);

56                     if(Find(st) == Find(ed)){

57                         int ans = road[j].pd - road[i].pd;  //舒适度

58                         min = ans < min ? ans : min;

59                         break;

60                     }

61                 }

62             }

63             if(min == inf)

64                 printf("-1\n");

65             else

66                 printf("%d\n",min);

67         }

68     }

69     return 0;

70 }