Entropy （huffman) 优先队列）

http://acm.hdu.edu.cn/showproblem.php?pid=1053

Huffman问题利用STL中的priority_queue解决；

 1 #include<stdio.h>

 2 #include<iostream>

 3 #include<string>

 4 #include<algorithm>

 5 #include<map>

 6 #include<queue>

 7 using namespace std;

 8 

 9 struct cmp

10 {

11     bool operator()(const int a, const int b)

12     {

13         return a > b;

14     }

15 };

16 int solve(string str)

17 {

18     priority_queue< int,vector<int>,cmp >que;

19     map<char, int> mymap;

20     int i;

21     for(i =0; i < str.size(); i++)

22     {

23         mymap[str[i]]++;

24     }

25 

26     map<char,int>::iterator it = mymap.begin();

27     while(it != mymap.end())

28     {

29         //printf("%c %d\n",it->first,it->second);

30         que.push(it->second);

31         it++;

32     }

33 

34     int weight = 0;

35     if(que.size() == 1)

36         return que.top();

37 

38     while(que.size() != 1)

39     {

40         int a,b;

41         a = que.top();

42         que.pop();

43         b = que.top();

44         que.pop();

45 

46         weight += a+b;

47         que.push(a+b);

48     }

49     return weight;

50 }

51 int main()

52 {

53     int weight;

54     string str;

55     while(cin>>str)

56     {

57         if(str == "END")

58             break;

59         weight = solve(str);

60         printf("%d %d %.1lf\n",8*str.size(),weight,8.0*str.size()/weight);

61     }

62     return 0;

63 }