Sort Colors

Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

You must solve this problem without using the library's sort function.

Example 1:

Input: nums = [2,0,2,1,1,0]
Output: [0,0,1,1,2,2]

Example 2:

Input: nums = [2,0,1]
Output: [0,1,2]

Constraints:

• n == nums.length
• 1 <= n <= 300
• nums[i] is either 0, 1, or 2.

Follow up: Could you come up with a one-pass algorithm using only constant extra space?

SOLUTION:

class Solution:
    def partition(self, nums, x, beg, end):
        i = beg
        for j in range(beg, end):
            if nums[j] <= x:
                nums[i], nums[j] = nums[j], nums[i]
                i += 1
        return i

    def sortColors(self, nums: List[int]) -> None:
        n = len(nums)
        i = self.partition(nums, 1, 0, n)
        self.partition(nums, 0, 0, i)
        return nums