CA 13 - Move Zeros

Problem Statement

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

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

Examples:

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

Input: nums = [0]
Output: [0]

Solution:
For this problem, my goal was to maintain the order of non-zero elements while moving all zeros to the end efficiently. I also wanted to solve it in-place without using any extra array, keeping the approach simple and optimal.

For the solution, I used a two-pointer approach. One pointer is used to track where the next non-zero element should be placed, and the other pointer is used to traverse the array. Whenever I find a non-zero element, I swap it with the position tracked by the first pointer and move that pointer forward. This way, all non-zero elements are shifted to the front in order, and zeros automatically end up at the back.

Solution Code (Python)

a = [0, 1, 0, 3, 12]

i = 0

for j in range(len(a)):
    if a[j] != 0:
        a[i], a[j] = a[j], a[i]
        i += 1

print(a)