Skip to main content

5. Remove Element

easyAsked at MercadoLibre

Remove all occurrences of a value from an array in place.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Return the number of elements in nums which are not equal to val.

Constraints

  • 0 <= nums.length <= 100
  • 0 <= nums[i], val <= 50

Examples

Example 1

Input
nums = [3,2,2,3], val = 3
Output
2, nums = [2,2,_,_]

Example 2

Input
nums = [0,1,2,2,3,0,4,2], val = 2
Output
5, nums = [0,1,4,0,3,_,_,_]

Approaches

1. Brute force

Filter into a new array.

Time
O(n)
Space
O(n)
const out = nums.filter(x => x !== val);
for (let i = 0; i < out.length; i++) nums[i] = out[i];
return out.length;

Tradeoff:

2. Two-pointer in place

Write pointer only advances for kept values.

Time
O(n)
Space
O(1)
function removeElement(nums, val) {
  let w = 0;
  for (let r = 0; r < nums.length; r++) {
    if (nums[r] !== val) nums[w++] = nums[r];
  }
  return w;
}

Tradeoff:

MercadoLibre-specific tips

MercadoLibre uses this to test write-pointer thinking — the same pattern they apply when scrubbing fraud-flagged transactions from in-memory batches.

Solve it now

Free. No sign-up. Python and JavaScript run instantly in your browser.

Output

Press Run or Cmd+Enter to execute

Practice these live with InterviewChamp.AI

Drill Remove Element and other MercadoLibre interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →