hdu 1598 find the most comfortable road

http://acm.hdu.edu.cn/showproblem.php?pid=1598

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #define maxn 2000

 5 using namespace std;

 6 const int inf=1<<30;

 7 

 8 int f[maxn],n,m,q,a,b;

 9 struct node

10 {

11     int u,v,w;

12     bool operator < (const node &a)const

13     {

14         return w<a.w;

15     }

16 }p[maxn];

17 

18 void inti()

19 {

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

21     {

22         f[i]=i;

23     }

24 }

25 

26 int find1(int x)

27 {

28     if(x==f[x]) return x;

29     return f[x]=find1(f[x]);

30 }

31 

32 void union1(int a,int b)

33 {

34     int fa=find1(a);

35     int fb=find1(b);

36     if(fa!=fb)

37     {

38         f[fa]=fb;

39     }

40 }

41 

42 int main()

43 {

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

45     {

46         for(int i=0; i<m; i++)

47         {

48             scanf("%d%d%d",&p[i].u,&p[i].v,&p[i].w);

49         }

50         sort(p,p+m);

51         scanf("%d",&q);

52         while(q--)

53         {

54             scanf("%d%d",&a,&b);

55             int min1=inf;

56             int j;

57             for(int i=0; i<m; i++)

58             {

59                 inti();

60                 for(j=i; j<m; j++)

61                 {

62                     union1(p[j].u,p[j].v);

63                     if(find1(a)==find1(b))

64                     {

65                         min1=min(min1,p[j].w-p[i].w);

66                          break;

67                     }

68                 }

69                 if(j==m) break;

70             }

71             if(min1==inf) printf("-1\n");

72             else

73                 printf("%d\n",min1);

74         }

75     }

76     return 0;

77 }

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