Binary Representation of Previous Number in JavaScript

Given a binary input of a positive number, our task is to find the binary representation of a number that is one less than a given binary number n in JavaScript.

Example:

Input: 100010
Output: 100001
Explanation: The decimal of 100010 is 34 and 100001 is 33.

Approach

• The function "previousBinary1" converts the input binary string to a decimal number using "parseInt(binary, 2)".
• It subtracts 1 from the decimal value to find the previous number.
• The function converts the resulting decimal number back to a binary string using "toString(2)".
• The resulting binary string, which represents the previous number, is returned by the function.
• The function call console.log(previousBinary1('100010')) prints the previous binary number, resulting in '100001'.

Example: The example below shows how to Find the binary representation of previous number using Brute Force Approach.

function previousBinary1(binary) {
    
    // Parse Binary to Decimal
    const decimal = parseInt(binary, 2);
    
    // Subtract 1
    const previousDecimal = decimal - 1;
    
    // Convert Back to Binary
    const previousBinary = previousDecimal.toString(2);
    
    return previousBinary;
}

console.log(previousBinary1('100010')); 

100001

Time Complexity: O(n)

Space Complexity: O(log M)

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Article Tags :

• JavaScript
• Web Technologies
• JavaScript-DSA