Sort Colors
Sort an array containing 0, 1, and 2 in-place 0 = red, 1 = white, 2 = blue Example: [2,0,2,1,1,0] => [0,0,1,1,2,2]
Sort Colors looks brute-forceable, but it's really about moving pointers with a reason. Interviewers love it because it reveals your invariant-driven scanning and your edge-case discipline. The trap is moving the wrong pointer and silently skipping the real answer.
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