Sort an Array of 0s, 1s and 2s

My Thought Process (Java DSA) When I came across this problem, it initially looked like a normal sorting problem. But the constraint made me rethink the approach. Problem understanding We are given an array arr[] containing only: 0s 1s 2s The task is to sort the array in ascending order without using any built-in sort function. Initial Thinking Let’s take an example: arr = [0, 1, 2, 0, 1, 2] Expected output: [0, 0, 1, 1, 2, 2] At first, the idea of using a sorting function came to mind. But since it is not allowed, I needed a different approach. Key Observation The array contains only three distinct values: 0 1 2 So instead of general sorting, I can group similar elements together. Approach (Dutch National Flag Algorithm) I used three pointers: low → to place 0s mid → to traverse the array high → to place 2s Logic i have been used for this problem If arr[mid] == 0 Swap with low, then increment both low and mid If arr[mid] == 1 Just move mid If arr[mid] == 2 Swap with high, then decreme