2020/4/3 CSC161
www.cs.grinnell.edu/~johnsonba/CSC161/2020S/homework/homework3.html 1/3
Home Schedule Class Slides Homework DeadlinesLabs and
Projects
CSC 161 - Imperative Problem
Solving
Homework 3 -
Calculating Maximum Hourglass
This homework is to be done individually. You may ask your instructor for help, but
do not ask other students, tutors, or mentors for assistance. You also may not refer
to any other materials to help you with this program, except for your textbook and
course website materials (if you use them, cite the reference).
This assignment is designed to give you practice in working with two-dimensional
arrays and bounds checking.
See the "Grading" section below for specific criteria for this assignment. As with all
projects and homework, the style guidelines apply to this assignment, and points
may be deducted for poor style, readability, and testing. Feedback will be given
using a version of this checklist.
Overview
This project will deal with a 6 x 6, two-dimensional array of integers (although it
would be pretty easy to extend this to an arbitrary sized array). The program will
traverse the two-dimensional array, A, calculating the sums of numbers located in a
particular pattern (the hourglass, defined below) surrounding each location A[i][j]
and reporting the greatest sum that is found.
This sort of array traversal and calculation may be found in a variety of situations,
such as reporting and updating the status of the squares surrounding characters in a
map-based videogame or in managing simulations of bacteria.
Input Format
For this assignment, we will stick with a 6 x 6 array of integers. The integers may
range from -9 to 9, including 0. As you read in the input, you must check that you
only encounter integers. If the user makes a mistake in input, you should print an
error message and quit.
The user will enter the array from standard input (stdin) as 6 rows of 6 integers, with
a space between each integer and a newline (return) character separating each row.
For instance:
1 0 0 0 0 0
2 1 0 0 0 0
3 2 1 0 0 0
2020/4/3 CSC161
www.cs.grinnell.edu/~johnsonba/CSC161/2020S/homework/homework3.html 2/3
4 3 2 1 0 0
5 4 3 2 1 0
6 5 4 3 2 1
Output Format
The program should output a single value: the largest of the hourglass sums. For the
example array above, your output might look like:
The largest hourglass sum is: 28
What Your Program Needs to Do
An hourglass is defined to be all the values in this pattern:
a b c
d
e f g
An hourglass sum is the result of adding all of the integers (a through g) in each
hourglass. In a 6 x 6 array, there are 16 hourglasses, and hence, there are 16 sums
to calculate. Since this calculation needs to be done repeatedly, this is a great place
to use a function!!
Testing
Test your program with both positive and negative values. You should also be sure to
test arrays that contain zeros.
Grading
I highly recommend that for this (and all coding projects) that you make a testing
plan before you start to write code. You do not need to plan to test all possible
inputs to the two programs, but you should have a plan that will test major sections
of your code and demonstrate your problem solving skills. Include this plan when
you submit your code and testing transcript.
Reminder: you may NOT use global variables for this or any subsequent
assignments; using a global variable will result in -5 points. Other stipulations are
found in the style guidelines.
The General Grading Form applies to this program project.
This project will be worth 20 points, based on the following criteria:
[1 point] Message to user about purpose of program
[1 point] Reminds user of the format for entering data
[2 points] Reads input from the user and checks that each entry is an integer
[2 points] Error message and exits if input is not correct
[3 points] Calculates the hourglasses using a function that takes the array as a
parameter
[3 points] Find the maximum hourglass in the array
[2 points] Prints result with explanation
2020/4/3 CSC161
www.cs.grinnell.edu/~johnsonba/CSC161/2020S/homework/homework3.html 3/3
[2 points] Ensures that the array bounds are checked while calculating the
hourglass sums
[4 points] Tests a variety of arrays containing positive and negative numbers as
well as zeros

This derivative work is used and licensed under a Creative Commons Attribution-NonCommercialShareAlike 4.0
International license. The original is by Henry Walker, except where noted; other material is provided by Jerod
Weinman and used with permission.