Update file AirlineProblem.java

Summary by Bito

This pull request addresses syntax and logic errors across multiple files. It fixes import statement formatting, conditional expressions, and adjustments to else block messaging in AirlineProblem.java, resolves arithmetic operations in BinaryConverter.java, and corrects assignment expressions in IntListVer2.java to enhance functionality, stability, and code clarity.

Unit tests added: False

Estimated effort to review (1-5, lower is better): 1