USACO Section 2.1: Ordered Fractions

 1 /*

 2 ID: leetcod3

 3 PROG: frac1

 4 LANG: C++

 5 */

 6 #include <iostream>

 7 #include <fstream>

 8 #include <string>

 9 #include <map>

10 #include <vector>

11 #include <set>

12 #include <algorithm>

13 #include <queue>

14 #include <cmath>

15 #include <list>

16 #include <cstring>

17 #include <cstdlib>

18 #include <limits>

19 #include <stack>

20 

21 using namespace std;

22 

23 ofstream fout ("frac1.out");

24 ifstream fin ("frac1.in");

25 

26 int N;

27 

28 int main()

29 {

30     fin >> N;

31     set<pair<int, int> > S, T;

32     for (int i = 1; i <= N; ++i) {

33         for (int j = 1; j <= i; ++j) {

34             if (S.find(make_pair(j, i)) == S.end()) {

35                 T.insert(make_pair(j, i));

36                 S.insert(make_pair(j, i));

37                 int k = 2;

38                 while (k * i <= N) {

39                     S.insert(make_pair(j*k, i*k));

40                     k++;

41                 }

42             }

43         }

44     }

45     T.insert(make_pair(0, 1));

46     map<double, pair<int, int> > H;

47     for (set<pair<int, int> >::iterator it = T.begin(); it != T.end(); it++) {

48         pair<int, int> tmp = *it;

49         H[(double)tmp.first*1.0/(tmp.second*1.0)] = tmp;

50     }

51     for (map<double, pair<int, int> >::iterator it = H.begin(); it != H.end(); it++)

52         fout << (it->second).first << "/" << (it->second).second << endl;

53     return 0;

54 }