DSA using JavaScript

Time Complexity: O(d), where d is the number of digits in the number. String and array operations are linear in the number of digits.
Space Complexity: O(d) Temporary storage for the string and reversed digits.

Maths

function reverseBruteForce(num) {
  const isNegative = num < 0;
  const reversedStr = Math.abs(num).toString().split("").reverse().join("");
  const reversedNum = parseInt(reversedStr, 10);
  return isNegative ? -reversedNum : reversedNum;
}

// Example Usage
console.log(reverseBruteForce(123));  // Output: 321
console.log(reverseBruteForce(-456)); // Output: -654
console.log(reverseBruteForce(100));  // Output: 1

function reverseEfficient(num) {
  let reversedNum = 0;
  const isNegative = num < 0;
  num = Math.abs(num);

  while (num > 0) {
    const digit = num % 10;
    reversedNum = reversedNum * 10 + digit;
    num = Math.floor(num / 10);
  }

  return isNegative ? -reversedNum : reversedNum;
}

// Example Usage
console.log(reverseEfficient(123));  // Output: 321
console.log(reverseEfficient(-456)); // Output: -654
console.log(reverseEfficient(100));  // Output: 1