CPSC 110-08: Computing on Mobile Phones Spring 2012 The Running Total Pattern Solutions to Exercises

CS Principles

• 15: The student can develop an algorithm.
• 16: The student can express an algorithm in a language.
• 20: The student can use abstraction to manage complexity in a program.

Exercises

• Modify the computeListSum function so that it computes the sum of only the odd numbers in a list. Name your new function computeListSumOdds.

  # Function to sum the odd numbers in a list # Argument: aList1 contains a list of integers To computeListSumOdds(aList1) : Set global Sum to 0 For each num1 in aList1 do: If the num1 is divisible by 2 then do: Set Sum to Sum + num1 Return Sum

1. Write and test a function named computeSumListFives that returns sum of the numbers that are multiples of 5 in a given list.

   # Function to calculate the sum of numbers divisible # by five in aList # Argument: aList contains a list of integers To computeSumListFives(aList) : Set global Sum to 0 For each number in aList do: If the number is divisible by 5 then do: Set Sum to Sum + number Return Sum

2. Write and test a function named countZeroes that will count the number of zeroes in a list. For example, if the list is [0 1 0 0 2 0 2], the function should return 4.

   # Function to count the number of 0s in a list # Argument: theList contains a list of integers To countZeroes(theList) : Set global count to 0 For each num in theList do: If the num = 0 then do: Set count to count + 1 Return Sum

3. The factorial of N is defined as N × N-1 × N-2 ... 2 × 1. Write a function to compute the factorial of N, where N is the argument. HINT: Try to see this as a running total problem.

   # Function to calculate the factorial of N # N! = N * (N-1) * (N-2) * ... * 2 * 1 # Argument: N, a positive number To factorial(N) : Set global product to 1 For each k in the range(1, N, 1) do: Set product to product × k Return product