Unit 4A - More Code Practice with Arrays

From CS Awesome 2CC BY-NC-SA 4.0 Original page

Java1 class period4 exercises8 graded tests

Files

Unit 4A - More Code Practice with Arrays

Each coding exercise has its own folder. Open its .java file and press Run to try it. Run Tests checks every graded exercise in this lesson at once.

Exercise 1

Create a method sum13(nums) that takes an array of integers, nums and returns the sum of the numbers in the array. However, the number 13 is very unlucky, so do not add it or the number that comes immediately after a 13 to the sum. Return 0 if nums is an empty array.

Example Input	Expected Output
`sum13({13, 1, 2})`	`2`
`sum13({1,13})`	`1`
`sum13({4, 13, 8})`	`4`
`sum13({13, 1, 13, 3, 2})`	`2`
`sum13({})`	`0`

Open the 01-sum13-written folder and edit Sum13.java. Press Run to try it; Run Tests checks it (2 tests).

Exercise 2

Create a method has22(nums) that takes an array of integers, nums and returns true if there are at least two items in the list that are adjacent and both equal to 2, otherwise return false.

Example Input	Expected Output
`has22({1, 2, 2})`	`true`
`has22({2, 1, 2})`	`false`
`has22({2, 2, 8})`	`true`
`has22({3, 3, 5})`	`false`

Open the 02-has22-written2 folder and edit Has22.java. Press Run to try it; Run Tests checks it (2 tests).

Exercise 3

Create the total89(nums) method below that takes an array of integers, nums, and returns the total of the numbers in nums except for all numbers in the array between an 8 and a 9 (inclusive).

Example Input	Expected Output
`total89({1, 2})`	`3`
`total89({2, 8, 3, 9, 2})`	`4`
`total89({8, 3, 5, 9, 6})`	`6`

Open the 03-total89-written folder and edit Total89.java. Press Run to try it; Run Tests checks it (2 tests).

Exercise 4

Create a method twoSum(nums, target) that takes an array of integers nums and an integer target and returns an array with the indices of two numbers such that they add up to target. If no two numbers add up to target, it returns an empty array. Assume that each input has exactly one solution, and you may not use the same element twice.

Example Input	Expected Output
`twoSum({2,7,11,15}, 9)`	`{0, 1}`
`twoSum({2,7,11,15}, 13)`	`{0, 2}`
`twoSum({2,7,11,15}, 5)`	`{}`

Open the 04-twoSum-written folder and edit TwoSum.java. Press Run to try it; Run Tests checks it (2 tests).

For teachers

Unit 4A - More Code Practice with Arrays

Students read CSAwesome2's “Unit 4A - More Code Practice with Arrays” in CS Room and work through its 4 Java coding exercises.

Time: 1 class period
Tests: 8 in 4 graded exercises, set up for you when you import the lesson

Goals

Practice for Unit 4: Data Collections.

Before class

Import the lesson into your class from the Lessons page, or with New assignment → Use a lesson. It arrives as a draft with its tests already set up.
Publish it.
The original page is on CS Awesome: https://runestone.academy/ns/books/published/csawesome2/MoreArrayPractice.html
CS Awesome's own teacher materials: the CS Awesome teacher site

In class

Students read README.md.
Students do exercises 01–04, each in its own folder, pressing Run to try their code.
Run Tests checks every graded exercise at once; scores appear in the Gradebook. Grading uses your copy of the tests, so a student who edits theirs does not change the grade.

Exercises

Folder	File	Grading	Tests
`01-sum13-written`	`Sum13.java`	Autograded	2
`02-has22-written2`	`Has22.java`	Autograded	2
`03-total89-written`	`Total89.java`	Autograded	2
`04-twoSum-written`	`TwoSum.java`	Autograded	2

Teachers can download a reference solution after signing in.