Sort 0s, 1s and 2s

Hi everyone! Today I solved a very interesting array problem where we need to sort an array containing only 0s, 1s, and 2s — but without using the built-in sort function. Problem Given an array of 0s, 1s, and 2s, sort it in ascending order. Example: Input: [0, 1, 2, 0, 1, 2] Output: [0, 0, 1, 1, 2, 2] My Approach At first, sorting seemed like the obvious solution. But the problem specifically says: Don’t use built-in sort So I looked for a better approach That’s when I learned about the Dutch National Flag Algorithm. Logic We use three pointers: low → for placing 0s mid → current element high → for placing 2s Rules: If element is 0 → swap with low, move both If element is 1 → just move mid If element is 2 → swap with high, move high Code (Python) class Solution: def sort012(self, arr): low, mid, high = 0, 0, len(arr) - 1 while mid <= high: if arr[mid] == 0: arr[low], arr[mid] = arr[mid], arr[low] low += 1 mid += 1 elif arr[mid] == 1: mid += 1 else: arr[mid], arr[high] = arr[high], a