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.

Following is an interesting method that uses queue data structure to print binary numbers. Thanks to Vivek for suggesting this approach.
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++

// 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 << "
"; 
  
        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; 
} 

Java

//Java program to generate binary numbers from 1 to n 
  
import java.util.LinkedList; 
import java.util.Queue; 
  
public class GenerateBNo  
{ 
    // This function uses queue data structure to print binary numbers 
    static void generatePrintBinary(int n) 
    { 
        // Create an empty queue of strings 
        Queue<String> q = new LinkedList<String>(); 
          
        // Enqueue the first binary number 
        q.add("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-- > 0) 
        { 
            // print the front of queue 
            String s1 = q.peek(); 
            q.remove(); 
            System.out.println(s1); 
              
            // Store s1 before changing it 
            String s2 = s1; 
              
            // Append "0" to s1 and enqueue it 
            q.add(s1 + "0"); 
              
            // Append "1" to s2 and enqueue it. Note that s2 contains 
            // the previous front 
            q.add(s2 + "1"); 
        } 
    } 
      
    // Driver program to test above function 
    public static void main(String[] args)  
    { 
        int n=10; 
        generatePrintBinary(n); 
    } 
} 
//This code is contributed by Sumit Ghosh 

Python

# Python program to generate binary numbers from  
# 1 to n  
  
# This function uses queu data structure to print binary numbers 
def generatePrintBinary(n): 
      
    # Create an empty queue 
    from Queue import Queue 
    q = Queue() 
      
    # Enqueu the first binary number 
    q.put("1") 
  
    # This loop is like BFS of a tree with 1 as root 
    # 0 as left child and 1 as right child and so on 
    while(n>0): 
        n-= 1 
        # Print the front of queue 
        s1 = q.get()  
        print s1  
      
        s2 = s1 # Store s1 before changing it 
      
        # Append "0" to s1 and enqueue it 
        q.put(s1+"0") 
  
        # Append "1" to s2 and enqueue it. Note that s2 
        # contains the previous front 
        q.put(s2+"1") 
      
  
# Driver program to test above function 
n = 10
generatePrintBinary(n) 
  
# This code is contributed by Nikhil Kumar Singh(nickzuck_007) 

C#

// C# program to generate binary 
// numbers from 1 to n  
using System; 
using System.Collections.Generic; 
  
class GFG 
{ 
    // This function uses queue data  
    // structure to print binary numbers  
    public static void generatePrintBinary(int n) 
    { 
        // Create an empty queue of strings  
        LinkedList<string> q = new LinkedList<string>(); 
  
        // Enqueue the first binary number  
        q.AddLast("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-- > 0) 
        { 
            // print the front of queue  
            string s1 = q.First.Value; 
            q.RemoveFirst(); 
            Console.WriteLine(s1); 
  
            // Store s1 before changing it  
            string s2 = s1; 
  
            // Append "0" to s1 and enqueue it  
            q.AddLast(s1 + "0"); 
  
            // Append "1" to s2 and enqueue it.  
            // Note that s2 contains the previous front  
            q.AddLast(s2 + "1"); 
        } 
    } 
  
    // Driver Code 
    public static void Main(string[] args) 
    { 
        int n = 10; 
        generatePrintBinary(n); 
    } 
} 
  
// This code is contributed by Shrikant13 

Output:

An Interesting Method to Generate Binary Numbers from 1 to n

C++

Java

Python

C#

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