Exercising these labs are of great fun. Hope you can enjoy, too.
Most of my solutions are quite efficient and well optimized, but you still can do more, don't settle. For promising CMU students, you should not read my code until lab due. For self-study students, you should try your best first. Discussion is welcome.
Efficient code optimization, observe general memory allocation pattern. My score is 98. I know there are 100s. try hard.
Know every detail of your program, like a writer of his novel. Robust error handling.