class Solution(object):
    def sortColors(self, nums):
        low = 0
        mid = 0
        high = len(nums) - 1
        
        while mid <= high:
            if nums[mid] == 0:
                # Found a red (0), move it to the left section
                nums[mid], nums[low] = nums[low], nums[mid]
                low += 1
                mid += 1
            elif nums[mid] == 1:
                # Found a white (1), it's already in correct position
                mid += 1
            else:  # nums[mid] == 2
                # Found a blue (2), move it to the right section
                nums[mid], nums[high] = nums[high], nums[mid]
                high -= 1
                # Don't increment mid as the swapped element needs checking

IE260_20210342_SeungyunShin.pptx