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Two Pointers
Easy

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.
10 min read
Solve on LeetCode
Examples
Input:nums = [0,1,0,3,12]
Output:[1,3,12,0,0]
Explain:

Non-zero elements are 1, 3, 12. They stay in that order. The 0s go to the end.

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

We need to push all 0s to the right side of the array.

Constraints:

  1. In-place: You cannot copy the valid numbers to a new array. You must do it inside nums.
  2. Relative Order: If 1 comes before 3 originally, it must stay that way.
  3. Minimize Operations: Ideally O(n) time.
Algorithm Strategy

We can use the Two Pointers technique to partition the array.

  • left pointer: Tracks the position where the next non-zero element should go.
  • right pointer: Scans the array to find non-zero elements.

Logic:

  1. Iterate through the array with right.
  2. If nums[right] is non-zero, we want to place it at nums[left].
  3. Swap nums[left] and nums[right]. Then left++.
  4. If nums[right] is zero, just continue scanning (right++).
Interactive Visualization
Step 1 / 5
L
R
0
0
1
1
0
2
3
3
12
4

Start: L=0, R=0.

1x
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