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5. Remove Element

easyAsked at GoDaddy

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

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

Problem

Given an array nums and a value val, remove all occurrences of val in-place. The order of remaining elements may change. Return the count of remaining elements k, and the first k slots of nums must hold them.

Constraints

  • 0 <= nums.length <= 100
  • 0 <= nums[i] <= 50
  • 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 to new array

Filter out val and write back into nums.

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

Tradeoff:

2. Two pointer write index

Maintain a write head; advance only when element != 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];
      k++;
    }
  }
  return k;
}

Tradeoff:

GoDaddy-specific tips

GoDaddy uses this style of in-place sweep to model pruning expired DNS records from a zone file array without re-sizing the buffer.

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Output

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