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5. Remove Element

easyAsked at Activision

Remove all instances of a value in-place — Activision uses it to gauge how you handle compaction of banned-player records.

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

Problem

Given an integer array and an integer val, remove all occurrences of val in-place. Return the count of remaining elements; order does not matter.

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 and copy

Filter into a new array, then copy back.

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

Tradeoff:

2. Two-pointer overwrite

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:

Activision-specific tips

Activision favors the in-place overwrite — they treat memory discipline as a proxy for how you'll think about per-match buffers in their multiplayer servers.

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Output

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