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5. Remove Element

easyAsked at Gojek

Remove all occurrences of a value in-place from an array and return the new length.

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 k of remaining elements; the first k slots of nums must contain the survivors in any order.

Constraints

  • 0 <= nums.length <= 100
  • 0 <= val <= 100

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

Approaches

1. Filter rebuild

Filter and write back.

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

Tradeoff:

2. Two pointers in-place

Write pointer advances only when current value isn't val; everything else gets overwritten.

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:

Gojek-specific tips

Gojek interviewers reward concise two-pointer solutions because their ride-status arrays churn frequently and need predictable mutation behavior.

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