Skip to main content

5. Remove Element

easyAsked at GitLab

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 every occurrence of val in-place. Return the count k of remaining elements; the first k slots of nums must hold the surviving values in any order.

Constraints

  • 0 <= nums.length <= 100
  • 0 <= val <= 100
  • Must be O(1) extra space

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=[0,1,3,0,4,_,_,_]

Approaches

1. Filter copy

Filter to a new array, copy back.

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

Tradeoff:

2. Two pointers

Write pointer advances only when value differs from val.

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];
  }
  return k;
}

Tradeoff:

GitLab-specific tips

GitLab often pivots this into a discussion of stable filtering for audit logs — be ready to say whether your approach preserves original ordering.

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 GitLab interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →