Move Zeroes

Photo by Scott Rodgerson on Unsplash

The other day I tried my hand at LeetCode problem 283: Move Zeroes. The directions were as follows:

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Example:

Input: [0,1,0,3,12]
Output: [1,3,12,0,0]

Note:

1. You must do this in-place without making a copy of the array.

2. Minimize the total number of operations.

First, I broke down the steps I could take to create this function.

1. Create a placeholder for the current position of the index.
2. Iterate through the given numbers. If the element at nums[i] is not 0, assign that number to the position of the placeholder.
3. Iterate through the rest of the remaining indices and assign them to 0.
4. Return the modified nums array.

Now that I have an idea of my code flow, I check to see for edge cases. If there are none, I can finally code the solution!

function moveZeroes(nums) {
  let position = 0;
  for (let i = 0; i < nums.length; i++) {
      if (nums[i] !== 0) {
          nums[position++] = nums[i];
      }
  }
  for (let i = position; i < nums.length; i++) {
      nums[i] = 0;
  }
  return nums
}

Success! The solution was accepted with a runtime of 80 ms — that’s faster than 93.86% of JavaScript online submissions for Move Zeroes. The memory usage, however, was 40.5 MB, which is less than 40.85% of JavaScript online submissions for this problem.

What is a solution you can come up with to improve memory usage? I’d love to know!