USACO Section 2.1: Hamming Codes

 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 }