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Algorithms & data structures medium

How to Sort Colors (Dutch National Flag) in Python

In-place sorting of a list of 0s, 1s, and 2s using the Dutch National Flag algorithm with O(n) time and O(1) space.

algorithm sorting two-pointers
Python 
def sort_colors(nums):
    low, mid, high = 0, 0, len(nums) - 1

    while mid <= high:
        if nums[mid] == 0:
            nums[low], nums[mid] = nums[mid], nums[low]
            low += 1
            mid += 1
        elif nums[mid] == 1:
            mid += 1
        else:  # nums[mid] == 2
            nums[mid], n…
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