Sort Colors 20 XP Medium

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Given an array with n objects colored red (0), white (1), and blue (2), sort them in-place so same colors are adjacent, in order: red, white, blue.

This is the famous Dutch National Flag problem by Dijkstra.

nums = [2,0,2,1,1,0] → [0,0,1,1,2,2]

Use three pointers: low (boundary for 0s), mid (current), high (boundary for 2s). One pass, O(n) time, O(1) space!

If nums[mid] == 0: swap with low, move both forward
If nums[mid] == 1: just move mid forward
If nums[mid] == 2: swap with high, move high back (don't move mid — the swapped value needs checking)

📋 Instructions

Implement `sort_colors(nums)` using the Dutch National Flag algorithm. Sort `[2,0,2,1,1,0]` in-place and print the result.

Three pointers: low=0, mid=0, high=len-1. While mid <= high, check nums[mid] and swap/move accordingly.

🧪 Test Cases

Input

sort_colors([2,0,2,1,1,0])

Expected

[0, 0, 1, 1, 2, 2]

Test case 1

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main.py

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Output

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