An Interesting Method to Generate Binary Numbers from 1 to n

Given a number n, write a function that generates and prints all binary numbers with decimal values from 1 to n.

Examples:

Input: n = 2
Output: 1, 10

Input: n = 5
Output: 1, 10, 11, 100, 101

A simple method is to run a loop from 1 to n, call decimal to binary inside the loop.
1) Create an empty queue of strings
2) Enqueue the first binary number “1” to queue.
3) Now run a loop for generating and printing n binary numbers.
……a) Dequeue and Print the front of queue.
……b) Append “0” at the end of front item and enqueue it.
……c) Append “1” at the end of front item and enqueue it.

Following is implementation of above algorithm.

// C++ program to generate binary numbers from 1 to n
#include <iostream>
#include <queue>
using namespace std;
// This function uses queue data structure to print binary numbers
void generatePrintBinary(int n)
{
    // Create an empty queue of strings
    queue<string> q;
    // Enqueue the first binary number
    q.push("1");
    // This loops is like BFS of a tree with 1 as root
    // 0 as left child and 1 as right child and so on
    while (n--)
    {
        // print the front of queue
        string s1 = q.front();
        q.pop();
        cout << s1 << "\n";
        string s2 = s1;  // Store s1 before changing it
  
        // Append "0" to s1 and enqueue it
        q.push(s1.append("0"));
        // Append "1" to s2 and enqueue it. Note that s2 contains
        // the previous front
        q.push(s2.append("1"));
    }
}
// Driver program to test above function
int main()
{
    int n = 10;
    generatePrintBinary(n);
    return 0;
}

Output:

1
10
11
100
101
110
111
1000
1001
1010

Disclaimer: This does not belong to TechCodeBit, its an article taken from the below
source and credits.
source and credits: http://www.geeksforgeeks.org
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rakesh

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