5. Remove Element

easyAsked at Electronic Arts

Remove all occurrences of a target value in place, returning the new logical length.

By Alex Chen, Founder, InterviewChamp.AI · Last verified 2026-05-20

Problem

Given an array nums and a value val, remove all instances of val in place. The relative order of elements may be changed and the first k slots must hold the remaining values.

Constraints

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

Examples

Example 1

Input

nums=[3,2,2,3], val=3

Output

k=2, nums=[2,2,_,_]

Example 2

Input

nums=[0,1,2,2,3,0,4,2], val=2

Output

k=5

Approaches

1. Filter into new array

Build a fresh array, then copy back.

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 pointers in place

Write pointer only advances on non-val reads, leaving valid prefix intact.

Time: O(n)
Space: O(1)

function removeElement(nums, val) {
  let k = 0;
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] !== val) {
      nums[k] = nums[i];
      k++;
    }
  }
  return k;
}

Tradeoff:

Electronic Arts-specific tips

EA gameplay engineers prefer the in-place pointer pass — it mirrors how entity arrays are compacted between frames in ECS pipelines.

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