Description

Problem Solving Session 2 – Functions and Array Basics

Notes to Student TAs:
It is important to show the coding process, which includes debugging, so there is no problem that you make a mistake. Sometimes it’s good for students to know how to trace a bug too.
It’d be good to let students see how you break down a problem and solve smaller problems (and make sure that they work) one at a time. Coding style (i.e., indentation & proper comments) is important too.
Problem 1
Write a void function OrderThreeIntegers() that takes three int arguments by reference. The function should determine the order of the values, and upon return of the function, it should modify the values in the arguments so that the first argument contains the largest value, the second the secondlargest, and the third the smallest value.
Write a simple driver program (i.e., main()) to test your functions. You should print out the values before and after calling OrderThreeIntegers() to show it works correctly.

Notes to Student TAs:
Concepts to reinforce here:
modularity by defining functions which serve specific purposes (or solve a smaller problem) in a program how a function prototype is defined based on the function purpose: return types and input arguments pass-by-value & pass-by-reference
Question: how many cases do you need to test if your program is correct? Answer: the input of 3 numbers can assume 3! = 6 permutations (or orders)
e.g., 1 2 3, 1 3 2, 2 1 3, 2 3 1, 3 1 2, 3 2 1 they all should result in an output 3 2 1
Problem 2
Write a program to read in a sequence of integers in the range from 0 to 10, and to find the mode of the input numbers (i.e., the number which occurs most frequently).
write a function int FindMax(int a[], int aSize) which returns the index of the largest element in the array a[]. The size of a[] is given by aSize.
if multiple elements have the same largest value, return the largest index of these elements.
write the main() function of the program:
define an array freq[] of 11 integers; each element will store the frequency of occurrences of an integer. For example, freq[i] stores the frequency of the number i in the input sequence. read a sequence of integers from user input which is terminated by a sentinel value -1. For each input integer, increment the corresponding frequency counter in the array freq[] outputs the frequencies of all numbers from 0 to 10, and output the mode of the input numbers.

Notes to Student TAs:
Concepts to reinforce here:
array as function parameter loop through an array for some processing
Question: Modify FindMax() so that if multiple elements have the same largest value, it returns the smallest index of these elements. Answer: change line 15 from if (a[i] >= a[maxIdx]) to if (a[i] > a[maxIdx])