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  1. #include <cassert>
  2. #include <cstdlib>
  3. #include <functional>
  4. #include <iostream>
  5. #include <string>
  6.  
  7. using Bits = std::string;
  8.  
  9. namespace {
  10.   void binary(int n, int k, std::function<void(Bits)> yield) {
  11.     if (k == 0) // no bits set
  12.       yield(Bits(n, '0'));
  13.     else if (n == k) // all bits set
  14.       yield(Bits(k, '1'));
  15.     else {
  16.       assert(n > k && k > 0);
  17.       binary(n - 1, k,     [&yield](Bits bits) { yield("0" + bits); });
  18.       binary(n - 1, k - 1, [&yield](Bits bits) { yield("1" + bits); });
  19.     }
  20.   }
  21. }
  22.  
  23.  
  24. int main() {
  25.   int n, k;
  26.   if(!(std::cin >> n >> k && n >= k && k >= 0))
  27.     exit(EXIT_FAILURE);
  28.  
  29.   binary(n, k, [](Bits bits) { std::cout << bits << '\n'; });
  30. }
  31.  
Success #stdin #stdout 0s 15232KB
comments (?)
stdin 
4
3
stdout 
0111
1011
1101
1110
https://ideone.com/Ay9yoa
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
secret

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