Sort Colors

Problem Given an array whose values are 0 (red), 1 (white), 2 (blue), sort it in place so equal colors are adjacent in red→white→blue order — in one pass, no library sort.

Input / Output

• Input: int array nums over {0,1,2}.
• Output: nums sorted in place.

Constraints

• n up to 3*10^5; the target is one pass with O(1) space (counting sort in two passes is the fallback).

Example

• [2,0,2,1,1,0] → [0,0,1,1,2,2]