Move all zeroes to the end while keeping the order of non-zero elements.

Interview question: Move Zeroes

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

- Move every `0` to the end of the array.
- Preserve the relative order of all non-zero values.
- The function returns the resulting array.

Understand the Goal

- Collect all non-zero values first.
- Count how many zeroes are needed at the end.
- This is easy to understand but uses extra space.

Simple Extra-Array Approach

- Keep a pointer for where the next non-zero value should be placed.
- Scan the array from left to right.
- Every non-zero value is written to the next available position, preserving order.

Use a Write Pointer

- After all non-zero values are written, everything from the write pointer to the end should be `0`.
- This produces the same array shape without needing a second array.
- Finally, return `nums`.

Fill the Remaining Positions with Zeroes

- The solution keeps non-zero elements in their original relative order.
- Time complexity is O(n).
- Space complexity is O(1) besides the input array.