USACO Section 2.1: Hamming Codes

dfs简单题

 1 /*

 2 ID: yingzho2

 3 PROG: hamming 

 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 ("hamming.out");

24 ifstream fin ("hamming.in");

25 

26 int N, B, D;

27 

28 bool check(int x, vector<int> &ans) {

29     for (int i = 0; i < ans.size(); ++i) {

30         int num = 0;

31         for (int j = 0; j < B; ++j) {

32             if (((x >> j) & 1) != ((ans[i] >> j) & 1)) num++;

33         }

34         if (num < D) return false;

35     }

36     return true;

37 }

38 

39 

40 void find(vector<int> &ans) {

41     if (ans.size() == N) return;

42     int x = ans[ans.size()-1] + 1;

43     while(ans.size() < N) {

44         if (check(x, ans)) {

45             ans.push_back(x);

46             find(ans);

47         }

48         else x++;

49     }

50 }

51 

52 int main()

53 {

54     fin >> N >> B >> D;

55     vector<int> ans;

56     ans.push_back(0);

57     find(ans);

58     int num = 0;

59     while (num < N-1) {

60         fout << ans[num];

61         if (num % 10 == 9) fout << endl;

62         else fout << " ";

63         num++;

64     }

65     fout << ans[N-1] << endl;

66     return 0;

67 }