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5. Remove Element

easyAsked at Wix

Remove all occurrences of a value in-place; Wix uses the pattern to strip deleted components from a published-site DOM array.

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

Problem

Given an array nums and a value val, remove all instances of val in-place. Return the number of elements not equal to val.

Constraints

  • 0 <= nums.length <= 100
  • 0 <= val, nums[i] <= 50

Examples

Example 1

Input
nums=[3,2,2,3], val=3
Output
2

Example 2

Input
nums=[0,1,2,2,3,0,4,2], val=2
Output
5

Approaches

1. Filter

Use Array.filter 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 pointers

Slow pointer writes kept values, fast pointer scans.

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:

Wix-specific tips

Wix likes when you mention the unstable order trick for cases where order doesn't matter — useful in their batch-cleanup jobs over per-tenant tables.

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Output

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