CSES 1668 Building Teams - Lessons

What did this problem add?

$1.$ Output the partition, not yes/no. The color array is the answer.

$2.$ Competitive programming I/O: read from stdin, print to stdout.

$3.$ Convert colors $0$/$1$ to team labels $1$/$2$ with +1.

$4.$ Handle the impossible case explicitly with "IMPOSSIBLE".

Three problems, same algorithm. The framing changes, but the core bipartite detection stays constant. You now have a template that works across platforms.