https://leetcode.com/problems/sort-colors/submissions/

sortColours.py

# First naiive attempt
class Solution:
    """
    :type nums: List[int]
    :rtype: void Do not return anything, modify nums in-place instead.
    """
    def sortColors(self, nums):
        pl = 0
        pr = len(nums)-1
        while pl < pr:
            if nums[pl] != 0:
                self.swap(nums, pl, pr)
                pr-=1
            if nums[pl] == 0:
                pl+=1

        if nums[pl] == 0:
            pl+=1
        pr = len(nums)-1

        while pl < pr:
            if nums[pl] != 1:
                self.swap(nums, pl, pr)
                pr-=1
            if nums[pl] == 1:
                pl+=1

    # After simplifying
    def sortColors2(self, nums):
        left = 0
        right = len(nums) - 1
        i = 0

        while(i <= right):
            if (nums[i] == 2 and i < right):
                self.swap(nums, i, right)
                right -= 1
            elif (nums[i] == 0 and i > left):
                self.swap(nums, i, left)
                left += 1
            else:
                i+=1
                
    # Utility methods
    def swap(self, array, i, j):
        tmp = array[i]
        array[i] = array[j]
        array[j] = tmp