Sort 0s, 1s, and 2s

Approach Explanation (o゜▽゜)o☆

1. I used three pointers: low=0, mid=0, and high=len(arr)-1.
2. I placed 0's at the beginning by swapping with low.
3. I left 1's in the middle.
4. I placed 2's at the end by swapping with high.
5. I repeated until mid-crossed high, and the array was sorted.

Methods Used ( ﾉ ^-^)ﾉ

• Dutch National Flag algorithm (single pass)
• Three-pointer technique (low, mid, high)
• Constant space (no extra array used)