Developing Procedures Practice Test

Based on the scenario, a student writes a procedure to find the maximum value in a non-empty list of integers. Input: list nums (length 1 to 50,000). Output: the largest integer in the list. Constraint: must work for negative numbers.

PROCEDURE maxValue(nums)

  max ← 0

  FOR EACH n IN nums

    IF n > max

      max ← n

    ENDIF

  ENDFOR

  RETURN max

ENDPROCEDURE

Which step is necessary to ensure the procedure works correctly for all valid inputs?

Based on the scenario, a teacher needs to count how many times each letter grade appears in a list grades containing strings from the set {"A","B","C","D","F"}. Input: list grades of length $n$. Output: a dictionary-like mapping from grade to count. Constraints: $n$ up to 200,000; only these five possible values; AP-style pseudocode.

A student writes:

PROCEDURE CountGrades(grades)

  counts <- {"A":0,"B":0,"C":0,"D":0,"F":0}

  FOR EACH g IN grades

    FOR EACH key IN counts

      IF g = key

        counts<u>key</u> <- counts<u>key</u> + 1

  RETURN counts

How can the procedure be optimized for better performance?