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5. Remove Element

easyAsked at Chime

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. The relative order may change. Return the number of elements that are not equal to val.

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

Approaches

1. Filter to new array

Build a new array excluding val and 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-pointer write index

Slow write pointer advances only when value is kept.

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:

Chime-specific tips

Chime regularly filters fraudulent or reversed transactions out of in-memory ledgers; demonstrate that you can mutate arrays in place without extra allocation.

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Output

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