Leetcode problem 5 - Number of Steps to Reduce a Number to Zero

Given an integer num, return the number of steps to reduce it to zero.

In one step, if the current number is even, you have to divide it by 2, otherwise, you have to subtract 1 from it.

Example 1:

Input: num = 14 Output: 6 Explanation: Step 1) 14 is even; divide by 2 and obtain 7. Step 2) 7 is odd; subtract 1 and obtain 6. Step 3) 6 is even; divide by 2 and obtain 3. Step 4) 3 is odd; subtract 1 and obtain 2. Step 5) 2 is even; divide by 2 and obtain 1. Step 6) 1 is odd; subtract 1 and obtain 0. Example 2:

Input: num = 8 Output: 4 Explanation: Step 1) 8 is even; divide by 2 and obtain 4. Step 2) 4 is even; divide by 2 and obtain 2. Step 3) 2 is even; divide by 2 and obtain 1. Step 4) 1 is odd; subtract 1 and obtain 0. Example 3:

Input: num = 123 Output: 12

/**
 * @param {number} num
 * @return {number}
 */
var numberOfSteps = function (num) {
  let count = 0;

  while (num !== 0) {
    if (num % 2 === 0) {
      num = num / 2;
      count++;
    }
    if (num % 2 === 1) {
      num--;
      count++;
    }
  }
  return count;
};

The function numberOfSteps takes a non-negative integer num as input and returns the number of steps required to reduce it to zero. The code enters a while loop that continues until num becomes zero. There are two conditional statements. The first one checks if num is even, and if it’s even, num is divided by 2, and count is incremented by 1. The second conditional statement checks if num is odd, and if it’s odd, num is decremented by 1, and count is incremented by 1. Ultimately, num will be zero and loop will be terminated, so count has number of iterates value.

Time complexity : O(log n) Space complexity : O(1)