Skip to main content

5. Remove Element

easyAsked at LINE

Remove all instances of a value from an array in place — LINE uses this as a stand-in for purging muted-user messages from a feed buffer.

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

Problem

Given an integer array nums and an integer val, remove all occurrences of val in place. Return the count of remaining elements; the first k slots of nums should hold them in any order.

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

Approaches

1. Filter to a new array

Build a new array without val, 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

Use a write pointer that advances only when the read value is not val.

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

Tradeoff:

LINE-specific tips

LINE expects you to mention that order can break for free here — same as when you tombstone deleted messages and don't re-sort the chat timeline.

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

Practice these live with InterviewChamp.AI →