Generate a random Binary String of length N

Given a positive integer N, the task is to generate a random binary string of length N.

Examples:

Input: N = 7
Output: 1000001

Input: N = 5
Output: 01001

Approach: The given problem can be solved by using the rand() function that generates a random number over the range [0, RAND_MAX] and with the help of the value returned by this function, any number in any range [L, R] can be generated as (rand() % (R - L + 1)) + L. Follow the steps below to solve the problem:

• Initialize an empty string, say S.
• Iterate over the range [0, N - 1] and perform the following steps:
  • Store a random number in the range [0, 1] using rand() function.
  • Append the randomly generated 0 or 1 to the end of the string S.
• After completing the above steps, print the string S as the resulting binary string.

Below is the implementation of the above approach:

// C++ program for the above approach

#include <bits/stdc++.h>
using namespace std;

// Function to find a random
// number between 0 or 1
int findRandom()
{
    // Generate the random number
    int num = ((int)rand() % 2);

    // Return the generated number
    return num;
}

// Function to generate a random
// binary string of length N
void generateBinaryString(int N)
{
    srand(time(NULL));

    // Stores the empty string
    string S = "";

    // Iterate over the range [0, N - 1]
    for (int i = 0; i < N; i++) {

        // Store the random number
        int x = findRandom();

        // Append it to the string
        S += to_string(x);
    }

    // Print the resulting string
    cout << S;
}

// Driver Code
int main()
{
    int N = 7;
    generateBinaryString(N);

    return 0;
}

// Java program for the above approach
class GFG{
    
// Function to find a random
// number between 0 or 1
static int findRandom()
{
    
    // Generate the random number
    int num = (1 + (int)(Math.random() * 100)) % 2;

    // Return the generated number
    return num;
}

// Function to generate a random
// binary string of length N
static void generateBinaryString(int N)
{
    
    // Stores the empty string
    String S = "";

    // Iterate over the range [0, N - 1]
    for(int i = 0; i < N; i++)
    {
        
        // Store the random number
        int x = findRandom();

        // Append it to the string
        S = S + String.valueOf(x);
    }

    // Print the resulting string
    System.out.println(S);
}

// Driver Code
public static void main (String[] args)
{
    int N = 7;
    
    generateBinaryString(N);
}
}

// This code is contributed by AnkThon

# Python3 program for the above approach
import random

# Function to find a random
# number between 0 or 1
def findRandom():
    
    # Generate the random number
    num = random.randint(0, 1)

    # Return the generated number
    return num

# Function to generate a random
# binary string of length N
def generateBinaryString(N):
    
    # Stores the empty string
    S = ""

    # Iterate over the range [0, N - 1]
    for i in range(N):
        
        # Store the random number
        x = findRandom()

        # Append it to the string
        S += str(x)
    
    # Print the resulting string
    print(S)

# Driver Code
N = 7

generateBinaryString(N)

# This code is contributed by sanjoy_62

// C# program for the above approach
using System;
using System.Collections.Generic;
using System.Linq;

public class GFG {
    
// Function to find a random
// number between 0 or 1
static int findRandom()
{
  
    // For random generator
    Random rand = new Random();
    
    // Generate the random number
    int num =  rand.Next() % 2;
 
    // Return the generated number
    return num;
}
 
// Function to generate a random
// binary string of length N
static void generateBinaryString(int N)
{
     
    // Stores the empty string
    string S = "";
 
    // Iterate over the range [0, N - 1]
    for(int i = 0; i < N; i++)
    {
         
        // Store the random number
        int x = findRandom();
 
        // Append it to the string
        S = S + x.ToString();
    }
 
    // Print the resulting string
    Console.WriteLine(S);
}


// Driver Code
public static void Main (string[] args)
{
    
    int N = 7;
    generateBinaryString(N);
}
}

// This code is contributed by code_hunt.

   <script>
   
        // Javascript program for the above approach

        // Function to find a random
        // number between 0 or 1
        function findRandom() {
            // Generate the random number
            let num = 
            (1 + parseInt((Math.random() * 100))) % 2;

            // Return the generated number
            return num;
        }

        // Function to generate a random
        // binary string of length N
        function generateBinaryString(N) {

            // Stores the empty string
            let S = "";

            // Iterate over the range [0, N - 1]
            for (let i = 0; i < N; i++) {

                // Store the random number
                let x = findRandom();

                // Append it to the string
                S += (x).toString();
            }

            // Print the resulting string
            document.write(S)
        }

        // Driver Code
        let N = 7;
        generateBinaryString(N);

        // This code is contributed by Hritik
        
    </script>

0101101

Time Complexity: O(N) In the above-given approach, there is one loop for iterating over string which takes O(N) time in worst case. Therefore, the time complexity for this approach will be O(N).
Auxiliary Space: O(N)// an extra variable store all the characters of the string and in worst case all characters will be unique hence algorithm takes up linear space