An Interesting Method to Generate Binary Numbers from 1 to n?

Here we will see one interesting method for generating binary numbers from 1 to n. Here we are using queue. Initially the queue will hold first binary number ‘1’. Now repeatedly delete element from queue, and print it, and append 0 at the end of the front item, and append 1 at the end of the front time, and insert them into the queue. Let us see the algorithm to get the idea.

Algorithm

genBinaryNumbers(n)

Begin
   define empty queue.
   insert 1 into the queue
   while n is not 0, do
      delete element from queue and store it into s1
      print s1
      s2 := s1
      insert s1 by adding 0 after it into queue
      insert s1 by adding 1 after it into queue
      decrease n by 1
   done
End

Example

#include <iostream>
#include <queue>
using namespace std;
void genBinaryNumbers(int n){
   queue<string> qu;
   qu.push("1");
   while(n != 0){
      string s1 = qu.front();
      qu.pop();
      cout << s1 << " ";
      string s2 = s1;
      qu.push(s1 + "0");
      qu.push(s1 + "1");
      n--;
   }
}
int main() {
   int n = 15;
   genBinaryNumbers(n);
}

Output

1 10 11 100 101 110 111 1000 1001 1010 1011 1100 1101 1110 1111