75. 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.


Note: Don't increment current pointer if find Blue or the color that goes to the right. Dutch National Flag.


def sortColors(nums):
    """
    Do not return anything, modify nums in-place instead.
    """
    red_next = 0
    blue_next = len(nums) -1
   
    def swap(i, j):
        nums[i], nums[j] = nums[j], nums[i]
       
    cur = 0
    while cur <= blue_next:            
        if nums[cur] == 0:
            swap(cur, red_next)
            red_next += 1
            cur += 1
        elif nums[cur] == 2:                
            swap(cur, blue_next)                
            blue_next -= 1
        else:
            cur += 1

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