Remove Element

Problem Statement

Given an array of integers and a target value, remove all occurrences of that value in-place and return the new length of the array.

The order of remaining elements does not need to be preserved. You do not need to worry about elements beyond the new length.

Function Signature:

function removeElement(arr, val) {
  // Your code here
}

Examples

Input	Value	Output	Array After
[3, 2, 2, 3]	3	2	[2, 2, ...]
[0, 1, 2, 2, 3, 0, 4, 2]	2	5	[0, 1, 3, 0, 4, ...]
[1]	1	0	[...]
[1]	2	1	[1]

Constraints

• Array length: 0 ≤ arr.length ≤ 100
• Element values: 0 ≤ arr[i] ≤ 50
• 0 ≤ val ≤ 100

Interactive Editor

function removeElement(arr, val) {
// Your code here

}

Tests: 6 total

Hints

Hint 1: Two Pointers

Use a "write pointer" to track where the next non-target element should go. Copy non-target elements to this position as you iterate.

Solution

View Solution Explanation

function removeElement(arr, val) {
  let writeIndex = 0;

  for (let i = 0; i < arr.length; i++) {
    if (arr[i] !== val) {
      arr[writeIndex] = arr[i];
      writeIndex++;
    }
  }

  return writeIndex;
}

Iterate through the array. When you find an element that's not the target, copy it to writeIndex and increment. The final writeIndex is the new length.

Complexity: O(n) time, O(1) space.