Grade 11 Java Review Part 2

Instructions

Program the solutions for each problem in a single Utility.java file in src/gr11review/part2 directory. You are required to:

a) Code Solutions

• within a group of two or three, each of your coding to your own branch, code your solutions in VS Code.
• Each member must pick a problem from each section (Methods, FileIO, Array - One Dimensional 1 Loop, Array - One Dimensional 2 Loops, Two Dimensional Arrays)
• commit and push changes to appropriate development branches in github.
• merge tested and completed solutions to the main branch.
• use proper style conventions for variable names and comments.

b) Test Solutions

• Create a test class UtilityTest.java in the src/gr11review/part2 directory.
• With the concepts of the Types of Tests, define test methods to thoroughly test the functionality of your solution methods.
• Name your test methods using the name of the solution method + "Test" + test case #. For example, if your solution method in Utility.java is called abc(), there should be corresponding test methods in UtilityTest.java called abcTest1(), abcTest2(), abcTest3() ... etc.
• tests methods should also be created by each member in their development branch and merged into the main branch.

Problem Sets

Methods

Methods 1

We'll say that a String is xy-balanced if for all the 'x' chars in the string, there exists a 'y' char somewhere later in the string. So "xxy" is balanced, but "xyx" is not. One 'y' can balance multiple 'x's. Return true if the given string is xy-balanced. Signature public static boolean xyBalance(String str)

Examples

xyBalance("aaxbby") → true
xyBalance("aaxbb") → false
xyBalance("yaaxbb") → false

Methods 2

Given a string, return the sum of the numbers appearing in the string, ignoring all other characters. A number is a series of 1 or more digit chars in a row. (Note: Character.isDigit(char) tests if a char is one of the chars '0', '1', .. '9'. Integer.parseInt(string) converts a string to an int.) Signature public static int sumNumbers(String str)

Examples

sumNumbers("abc123xyz") → 123
sumNumbers("aa11b33") → 44
sumNumbers("7 11") → 18

Methods 3

Given a string, does "xyz" appear in the middle of the string? To define middle, we'll say that the number of chars to the left and right of the "xyz" must differ by at most one. Signature public static boolean xyzMiddle(String str)

Examples

xyzMiddle("AAxyzBB") → true
xyzMiddle("AxyzBB") → true
xyzMiddle("AxyzBBB") → false

File IO

File IO - Read 1

Write a method longestWord(String filenametxt) such that given the name of a file filenametxt that contains a single word on each line, returns the longest word in the file.
Signature public static String longestWord(String filenametxt)

Example

words.txt contains:

Lorem
ipsum
dolor
sit
amet
consectetur
adipiscing 
elit

longestWord("words.txt") --> consectetur

File IO - Read 2

Write a method alphaWord(String filenametxt) such that given the name of a file filenametxt that contains a single word on each line, returns the word that is alphabetically first.
Signature public static String alphaWord(String filenametxt)

Example

words.txt contains:

Lorem
ipsum
dolor
sit
amet
consectetur
adipiscing 
elit

alphaWord("words.txt") --> amet

File IO - Read 3

Write a method vowelCount(String filenametxt) such that given the name of a file filenametxt that contains a single word on each line, returns the word that has the highest count of vowels.
Signature public static String vowelCount(String filenametxt)

Example

words.txt contains:

Lorem
ipsum
dolor
sit
amet
consectetur
adipiscing 
elit

vowelCount("words.txt") --> consectetur

Arrays - One Dimensional, 1 Loop

Array 1 - One Dimensional

Return a version of the given array where all the 10's have been removed. The remaining elements should shift left towards the start of the array as needed, and the empty spaces a the end of the array should be 0. So {1, 10, 10, 2} yields {1, 2, 0, 0}. You may modify and return the given array or make a new array. Signature public static int[] withoutTen(int[] nums)

Examples

withoutTen([1, 10, 10, 2]) → [1, 2, 0, 0]
withoutTen([10, 2, 10]) → [2, 0, 0]
withoutTen([1, 99, 10]) → [1, 99, 0]

Array 2 - One Dimensional

We'll say that an element in an array is "alone" if there are values before and after it, and those values are different from it. Return a version of the given array where every instance of the given value which is alone is replaced by whichever value to its left or right is larger. public int[] notAlone(int[] nums, int val)
Signature public static int[] notAlone(int[] nums, int value)

Examples

notAlone([1, 2, 3], 2) → [1, 3, 3]
notAlone([1, 2, 3, 2, 5, 2], 2) → [1, 3, 3, 5, 5, 2]
notAlone([3, 4], 3) → [3, 4]

Array 3 - One Dimensional

Return an array that contains the exact same numbers as the given array, but rearranged so that all the zeros are grouped at the start of the array. The order of the non-zero numbers does not matter. So {1, 0, 0, 1} becomes {0 ,0, 1, 1}. You may modify and return the given array or make a new array.
Signature public static int[] zeroFront(int[] nums)

Examples

zeroFront([1, 0, 0, 1]) → [0, 0, 1, 1]
zeroFront([0, 1, 1, 0, 1]) → [0, 0, 1, 1, 1]
zeroFront([1, 0]) → [0, 1]

Arrays - One Dimensional, 2 Loops

Array 4 - One Dimensional - Two Loops

Given two arrays of ints sorted in increasing order, outer and inner, return true if all of the numbers in inner appear in outer. The best solution makes only a single "linear" pass of both arrays, taking advantage of the fact that both arrays are already in sorted order.
Signature public static boolean linearIn(int[] outer, int[] inner)

Examples

linearIn([1, 2, 4, 6], [2, 4]) → true
linearIn([1, 2, 4, 6], [2, 3, 4]) → false
linearIn([1, 2, 4, 4, 6], [2, 4]) → true

Array 5 - One Dimensional - Two Loops

Given a non-empty array, return true if there is a place to split the array so that the sum of the numbers on one side is equal to the sum of the numbers on the other side.
Signature public static boolean canBalance(int[] nums)

Examples

canBalance([1, 1, 1, 2, 1]) → true
canBalance([2, 1, 1, 2, 1]) → false
canBalance([10, 10]) → true

Array 6 - One Dimensional - Two Loops

Given n>=0, create an array with the pattern {1, 1, 2, 1, 2, 3, ... 1, 2, 3 .. n} (spaces added to show the grouping). Note that the length of the array will be 1 + 2 + 3 ... + n, which is known to sum to exactly n*(n + 1)/2.
Signature public static int[] seriesUp(int n)

Examples

seriesUp(3) → [1, 1, 2, 1, 2, 3]
seriesUp(4) → [1, 1, 2, 1, 2, 3, 1, 2, 3, 4]
seriesUp(2) → [1, 1, 2]

Arrays - Two Dimensional

Array 7 - Two Dimensional

Write a method that takes a 2D array and reverses all of the content in the 2D array. The last value should be the first, and the first value should be the last.

Signature public static int[][] reverse(int[][] arr)

Example

reverse({{1,2,3},{4,5,6},{7,8,9}}) returns

[9,8,7]
[6,5,4]
[3,2,1]

Array 8 - Two Dimensional

Write a method that returns a portion of a 2D array based on a specified row and col.
Signature public static int[][] split(int[][] arr, int row, int col)

Example

For example, the call split({{1,2,3},{4,5,6},{7,8,9}}, 1, 1) would return all elements up to that point in the 2D array:

[1,2]
[4,5]

Array 9 - Two Dimensional

Write a method that inverts a 2D array. Inverting a 2D array means that each row of the 2D array is now a column, and each column is now a row.

Signature public static int[][] invert(int[][] arr)

Example

If we were to invert the 2D array:

[1,1,1]
[2,2,2]
[3,3,3]

the result would be:

[1,2,3]
[1,2,3]
[1,2,3]