LeetCode August - Day 21

Problem Statement

Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A.

You may return any answer array that satisfies this condition.

Example 1:

Input: [3,1,2,4]
Output: [2,4,3,1]

The outputs [4,2,3,1], [2,4,1,3], and [4,2,1,3] would also be accepted.

Note:
1 <= A.length <= 5000
0 <= A[i] <= 5000

Code (easy naive/bruteforce solution)

function sortArrayByParity(A){
  const even = [], odd = [];
  for(let x in A){
    if(x % 2) odd.push(x);
    else even.push(x);
  }
  return [...even, ...odd];
}

Time complexity: O(N)
Space complexity: O(N)

Code (two pointers)

function sortArrayByParity(A){
  if(A.length < 2) return [...A];

  let i = 0, j = A.length - 1;
  while(i < j){
    if(A[j] % 2 < A[i] % 2){
      [A[i], A[j]] = [A[j], A[i]];
    }

    if(A[i] % 2 === 0) i++;
    if(A[j] % 2 === 1) j--;
  }
  return A;
}

Time complexity: O(N)
Space complexity: O(1)