My friend is a C++ guy. The guy who gave him these assignments is a Taiwanese. My friend told me that these questions looks easy, but it is by no means some simple exercises. Though it is an open test (for this weekend), C++ experts can judge your level from your code.
I am Java-oriented, so I don't sell my C++ story. But I have some comments on 3 and 4. The best solution for 3 is to use java.io.PipedInputStream and java.io.PipedOutputStream ... But people can also create the wheels themselves. The simplest solution for 4 is to use java.awt.Graphics to draw lines. If you can use Java 2D to implement it, you may give people a deeper impression. Even for these simple examples, people can judge how good you are at programming from the following aspects: Is the scope of variables in your code reasonable? If your code flexible? .....