Checkpoint 2 — Contest 2 Practice

This is a practice paper modelled on ACSL Contest 2: short-answer questions from the four Contest 2 categories, then one programming problem. The Junior paper and the Intermediate/Senior paper share their first four questions, so this checkpoint holds both six-question papers.

Choose your path.

• Junior: Questions 1–6, then Question 9.
• Intermediate or Senior: Questions 1–4 and 7–8, then Question 9. Questions 5–6 are optional extra loop practice.
• Classroom (no programming): Questions 1–4 and 7–8. Questions 5–6 are optional, and Question 9 is left out.

Take it as a timed practice.

• Put away your notes and set a timer.
• Give yourself 30 minutes for the six-question paper on your path, as in the real contest. Work with pencil and paper only: no computer, no calculator. Write each answer on paper or in your notebook.
• On the Junior, Intermediate or Senior path, then give yourself about 60 minutes for Question 9 (the Classroom path skips it). Write a complete program that reads the input with input() and prints exactly the output described. Save it as a .py file and run it from a terminal, typing the sample input or feeding it a file: python my_solution.py < sample.txt. Print nothing extra: no prompts in input(), and no words the problem did not ask for.

These times are a practice pace, not the official rules; the real limits for your division are published by ACSL at acsl.org.

How to write short answers.

• Give exactly one answer, written the way the question asks for it.
• For a prefix or postfix expression, separate the tokens with single spaces and keep the operands in their original order.
• For a numeric value, write a whole number when the value is whole, and otherwise a decimal such as 13.5.
• For a bit string, write every bit, at the full length given in the question.
• For a list of bit strings, write them from smallest to largest, separated by a comma and a space.
• For a LISP list, write it in parentheses with single spaces, such as (A B C), using the capital letters the question uses.
• For a program, write exactly the one line it outputs.

When you finish, check yourself.

• Short answers have no sample to test against. Mark the questions you were unsure of, then work each one again by its unit's method: redo the stack or the trace, or turn a conversion back and check that you get the question. Compare with a partner, or with a second attempt made without looking at the first.
• The programming question is checked against its sample, and against inputs of your own made from its constraints: the smallest cases, the largest, and the tricky ones.

Then go back to the unit for any category that cost you points.