Frequent Terms

Frequency Counting of Words / Top N words in a document.

 

Given N terms, your task is to find the k most frequent terms from given N terms.

 

Input format :

 

First line of input contains N, denoting the number of terms to add.

In each of the next N lines, each contains a term.

Next line contains k, most frequent terms.

 

Output format :

 

Print the k most frequent terms in descending order of their frequency. If two terms have same frequency print them in lexicographical order.

 

Sample input :

 

14

Fee

Fi

Fo

Fum

Fee

Fo

Fee 

Fee

Fo

Fi

Fi

Fo

Fum

Fee

3

 

Sample output :

 

Fee

Fo

Fi

 

Constraint :

0 < N < 300000 

0 < term length < 25.

比较函数不要引用。

 1 #include <iostream>

 2 #include <algorithm>

 3 #include <string>

 4 using namespace std;

 5 

 6 struct Node

 7 {

 8     string name;

 9     int count;

10 };

11 

12 string strs[300001];

13 Node items[300001];

14 int GetCounts(int &num)

15 {

16     if(num <= 0) return false;

17     sort(strs, strs+num);

18     string tempStr = strs[0];

19     int counts = 0;

20     int i,j;

21     for(j = i = 0; i < num; ++i, ++counts)

22     {

23         if(strs[i] != tempStr)

24         {

25             items[j].count = counts;

26             items[j].name = tempStr;

27             tempStr = strs[i];

28             counts = 0;

29             j++;

30         }

31     }

32     items[j].name = tempStr;

33     items[j].count = counts;

34     return j+1;

35 }

36 bool compareNode(const Node a, const Node b)

37 {

38     if(a.count == b.count)

39         return a.name <= b.name;

40     return a.count > b.count;

41 }

42 bool GetAnswer(int num)

43 {

44     int k;

45     cin >> k;

46     sort(items,items+num, compareNode);

47     for(int i = 0;i < k; i++)

48         cout << items[i].name << endl;

49     return true;

50 }

51 int main()

52 {

53     int num;

54     while(cin >> num)

55     {

56         for(int i = 0; i < num; ++i)

57             cin >> strs[i];

58         int uniqueNum = GetCounts(num);

59         GetAnswer(uniqueNum);

60     }

61     return 0;

62 }