hdu Disjoint-set problems

Disjoint-set namely Union-Find set!

hdu 3172 virtual friends  http://acm.hdu.edu.cn/showproblem.php?pid=3172

Yes! A very interesting problem!

Whenever a friendship is formed,printf the number of the peoplein the social network.

OK, I failed lots of time. And all are "Time Limit Exceeded".

But to my surprise!  I just replace the "cin" with “scanf” ,"cout" with "printf" in the code,and accepted!

learned:  scanf/printf  is more efficient than cin/cout;

View Code

 1 #include<iostream>

 2 #include<cstring>

 3 #include<string>

 4 #include<map>

 5 #include<cstdio>

 6 using namespace std;

 7 int f[200005],num[200005];

 8 void sequence()

 9 {

10     int i;

11     for(i=1;i<200005;i++)

12     {

13         f[i]=i;

14         num[i]=1;

15     }

16 }

17 int find(int x)

18 {

19     if(x!=f[x])

20         f[x]=find(f[x]);

21     return f[x];

22 

23 }

24 void Union(int x,int y)

25 {

26      x=find(x);

27      y=find(y);

28      if(x==y)

29      {

30          printf("%d\n",num[x]);

31      }

32      else

33      {

34          f[y]=x;

35          num[x]+=num[y];

36         printf("%d\n",num[x]);

37      }

38 }

39 int main()

40 {

41     int t;

42     map<string,int>match;

43     while(scanf("%d",&t)!=EOF)

44     {

45         int k;

46         string name1,name2;

47         while(t--)

48         {

49             sequence();

50             match.clear();

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

52             int s=1;

53             while(k--)

54             {

55                 cin>>name1>>name2;

56                 if(match.find(name1)==match.end())

57                 {

58                     s++;match[name1]=s;

59                 }

60                 if(match.find(name2)==match.end())

61                 {

62                     s++;match[name2]=s;

63                 }

64                 Union(match[name1],match[name2]);

65             }

66         }

67     }

68     return 0;

69 }

70 

71             

72             

73 

74         

Post by heat_nan             @2013-03-17       12:03