Parity Sorting

LeetCode

Given an array of integers arr, modify it in place to put all even numbers before all odd numbers. The relative order between even numbers does not matter. Same for the odd numbers.

Example 1:

  • Input: arr = [3, 1, 2, 4, 6]
  • Output: [2, 4, 6, 1, 3]
  • Explanation: [4, 2, 6, 3, 1] is also accepted.

Example 2:

  • Input: arr = [1, 1, 1, 1]
  • Output: [1, 1, 1, 1]
1def sortArrayByParity(nums: List[int]) -> List[int]:
2    l, r = 0, len(nums) - 1
3    
4    while l < r:
5        if nums[l] % 2 == 0:
6            l += 1
7        elif nums[r] % 2 == 1:
8            r -= 1
9        else:
10            nums[l], nums[r] = nums[r], nums[l]
11            l += 1
12            r -= 1
13            
14    return nums
Previous
Merge Sorted Array
Next
Quicksort Partition
l
3
0
1
1
2
2
4
3
r
6
4
Step 1 / 6
Step 1:
Initialize pointers l=0, r=4.
Pointers: l=0, r=4
Focus: select @ [0, 4]