Description

Problems for exercises and homework for the “JavaScript Advanced” course @ SoftUni. Submit your solutions in the SoftUni judge system at https://judge.softuni.bg/Contests/1798/Exercise-Arrays.
1. Print an Array with a Given Delimiter
The input comes as an array of strings. The last element of the array is the delimiter.
The output is the same array, printed on the console, each element separated from the others by the given delimiter.
Examples
Input Output
Input Output
[‘One’,
‘Two’,
‘Three’, ‘Four’,
‘Five’,
‘-‘] One-Two-ThreeFour-Five [‘How about no?’, ‘I’,
‘will’,
‘not’,
‘do’,
‘it!’,
‘_’] How about no?_I_will_not_do_it!
2. Print Every N-th Element from an Array
The input comes as an array of strings. The last element is N – the step.
The output is every element on the N-th step starting from the first one. If the step is “3”, you need to print the 1-st, the 4-th, the 7-th … and so on, until you reach the end of the array. The elements must be printed each on a new line.
Example
Input Output
Input Output Input Output
[‘5′,
’20’,
’31’,
‘4’,
’20’,
‘2’] 5
31
20 [‘dsa’,
‘asd’,
‘test’,
‘tset’,
‘2’]
dsa test [‘1’,
‘2’,
‘3’,
‘4’,
‘5’,
‘6’] 1
Hints
• Use what you’ve seen from the previous problem to extract the last element of the array.
• Create a step variable to hold the given step of the array. Then print all the elements with a for loop, incrementing the loop variable with the value of the step variable.
3. Add and Remove Elements from an Array
Write a JS function that adds and removes numbers to / from an array. You will receive a command which can either be “add” or “remove”.
The initial number is 1. Each input command should increase that number, regardless of what it is.

Upon receiving an “add” command you should add the current number to your array.
Upon receiving the “remove” command you should remove the last entered number, currently existent in the array.
The input comes as an array of strings. Each element holds a command.
The output is the array itself, with each element printed on a new line. In case of an empty array, just print “Empty”.
Examples
Input Output
Input Output Input Output
[‘add’,
‘add’,
‘add’,
‘add’]
1
2
3
4 [‘add’,
‘add’,
‘remove’,
‘add’,
‘add’] 1
4
5 [‘remove’,
‘remove’,
‘remove’] Empty
4. Rotate Array
Write a JS function that rotates an array. The array should be rotated to the right side, meaning that the last element should become the first, upon rotation.
The input comes as an array of strings. The last element of the array is the amount of rotation you need to perform.
The output is the resulted array after the rotations. The elements should be printed on one line, separated by a single space.
Examples
Input Output
Input Output
[‘1’,
‘2’,
‘3’,
‘4’,
‘2’] 3 4 1 2 [‘Banana’,
‘Orange’,
‘Coconut’,
‘Apple’,
’15’] Orange Coconut Apple Banana
Hints
• Check if there is a built-in function for inserting elements at the start of the array.
5. Extract Increasing Subsequence from an Array
Write a function that extracts only those numbers that form a non-decreasing subsequence. In other words, you start from the first element and continue to the end of the given array of numbers. Any number which is LESS THAN the current biggest one is ignored, alternatively if it’s equal or higher than the current biggest one you set it as the current biggest one and you continue to the next number.
The input comes as an array of numbers.
The output is the processed array after the filtration, which should be a non-decreasing subsequence. Each element should be printed on a new line.
Examples
Input Output
Input Output Input Output
[1,
3,
8,
4,
10,
12,
3,
2,
24] 1
3
8
10
12
24 [1,
2,
3,
4] 1
2
3
4 [20,
3,
2,
15,
6,
1] 20
Hints
• The Array.reduce() built-in function might help you a lot with this problem.
6. Sort an Array by 2 Criteria
Write a function that orders a given array of strings, by length in ascending order as primary criteria, and by alphabetical value in ascending order as second criteria. The comparison should be case-insensitive.
The input comes as an array of strings.
The output is the ordered array of strings.
Examples
Input Output
Input Output Input Output
[‘alpha’,
‘beta’,
‘gamma’] beta alpha gamma [‘Isacc’,
‘Theodor’,
‘Jack’,
‘Harrison’,
‘George’]
Jack
Isacc
George
Theodor
Harrison
[‘test’,
‘Deny’,
‘omen’,
‘Default’] Deny omen test
Default
Hints
• An array can be sorted by passing a comparing function to the Array.sort() function.
• Creating a comparing function by 2 criteria can be achieved by first comparing by the main criteria, if the 2 items are different (the result of the compare is not 0) – return the result as the result of the comparing function. If the two items are the same by the main criteria (the result of the compare is 0), we need to compare by the second criteria and the result of that comparison is the result of the comparing function.
• You can check more about Array.sort() here – https://developer.mozilla.org/enUS/docs/Web/JavaScript/Reference/Global_Objects/Array/sort
Multidimensional Arrays (Matrices)
We will mainly work with 2-dimensional arrays. The concept is as simple as working with a simple 1dimensional array. It is just an array of arrays.
7. Magic Matrices
Write a function that checks if a given matrix of numbers is magical. A matrix is magical if the sums of the cells of every row and every column are equal.
The input comes as an array of arrays, containing numbers (number 2D matrix). The input numbers will always be positive.
The output is a Boolean result indicating whether the matrix is magical or not.
Examples

Input Output
[[4, 5, 6],
[6, 5, 4],
[5, 5, 5]] true

Input Output Input Output
[[11, 32, 45],
[21, 0, 1],
[21, 1, 1]] false [[1, 0, 0],
[0, 0, 1],
[0, 1, 0]] true

8. *Tic-Tac-Toe
Make a tic-tac-toe console application.
You will receive an array of arrays. As you know there are two players in this game, so the first element of the input will be first player’s chosen coordinates, the second element will be the second player’s turn coordinates and so on. The initial state of the dashboard is
[[false, false, false],
[false, false, false],
[false, false, false]]
The first player’s mark is X and the second player’s mark is O.
Input
One parameter:
• An array – the moves in row that players make
Output
• There are two players – X and O
• If a player tries to make his turn on already taken place, he should make his turn again and you should print the following message:
“This place is already taken. Please choose another!”
• If there are no free spaces on the dashboard and nobody wins the game should end and you should print the following message:
“The game ended! Nobody wins :(”
• If someone wins you should print the following message and the current state of the dashboard:
“Player {X/0} wins”
Note: When printing the state of the dashboard the elements of each row the dashboard should be separated by ” ” and each row should be on new line.

Constraints
The elements in the input array will always be enough to end the game.
Examples
Input Output
[“0 1”,
“0 0”,
“0 2”,
“2 0”,
“1 0”,
“1 1”,
“1 2”,
“2 2”,
“2 1”,
“0 0”] Playe
O
X
O r O wins!
X X
O X false O
[“0 0”,
“0 0”,
“1 1”,
“0 1”,
“1 2”,
“0 2”,
“2 2”,
“1 2”,
“2 2”,
“2 1”] This place is already taken. Please choose another! Player X wins!
X X X false O O
false false false
[“0 1”,
“0 0”,
“0 2”, The g
O
X ame en
X
X ded! Nobody wins 🙁
X
O
“2 0”,
“1 0”,
“1 2”,
“1 1”,
“2 1”,
“2 2”,
“0 0”] O O X

9. **Diagonal Attack
Write a JS function that reads a given matrix of numbers and checks if both main diagonals have equal sum. If they do, set every element that is NOT part of the main diagonals to that sum, alternatively just print the matrix unchanged.
The input comes as array of strings. Each element represents a string of numbers, with spaces between them. Parse it into a matrix of numbers, so you can work with it.
The output is either the new matrix, with all cells not belonging to a main diagonal changed to the diagonal sum or the original matrix, if the two diagonals have different sums. You need to print every row on a new line, with cells separated by a space. Check the examples below.
Example

Input Output
Input Output
[‘5 3 12 3 1′,
’11 4 23 2 5’,
‘101 12 3 21
10’,
‘1 4 5 2 2’,
‘5 22 33 11 1’] 5 15 15 15 1
15 4 15 2 15
15 15 3 15 15
15 4 15 2 15
5 15 15 15 1 [‘1 1 1’,
‘1 1 1’
‘1 1 0’]
1 1 1
1 1 1
1 1 0
10. *Orbit
You will be given an empty rectangular space of cells. Then you will be given the position of a star. You need to build the orbits around it.
You will be given a coordinate of a cell, which will always be inside the matrix, on which you will put the value – 1. Then you must set the values of the cells directly surrounding that cell, including the diagonals, to 2. After which you must set the values of the next surrounding cells to 3 and so on. Check the pictures for more information.
For example, we are given a matrix which has 5 rows and 5 columns, and the star is at coordinates – 0, 0. Then the following should happen:
1 1 2 1 2 3 4 5

2 2

2 2 3 4 5
3 3 3 4 5
4 4 4 4 5
5 5 5 5 5

If the coordinates of the star are somewhere in the middle of the matrix for example – 2, 2, then it should look like this:
3 3 3 3 3
2 2 2 3 2 2 2 3
1 2 1 2 3 2 1 2 3
2 2 2 3 2 2 2 3
3 3 3 3 3

The input comes as an array of 4 numbers [width, height, x, y] which represents the dimensions of the matrix and the coordinates of the star.
The output is the filled matrix, with the cells separated by a space, each row on a new line.
Examples
Input Output
Input Output
Input Output
[4, 4, 0, 0] 1 2 3 4
2 2 3 4
3 3 3 4
4 4 4 4 [5, 5, 2, 2]
3 3 3 3 3
3 2 2 2 3
3 2 1 2 3
3 2 2 2 3
3 3 3 3 3 [3, 3, 2, 2] 3 3 3
3 2 2
3 2 1
Hints
• Check if there is some dependency or relation between the position of the numbers and the rows and columns of those positions.

11. *Spiral Matrix
Write a JS function that generates a Spirally-filled matrix with numbers, with given dimensions.
The input comes as 2 numbers that represent the dimension of the matrix.
The output is the matrix filled spirally starting from 1. You need to print every row on a new line, with the cells separated by a space. Check the examples below.
Examples
Input Output
Input Output
5, 5 1 2 3 4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9 3, 3 1 2 3
8 9 4
7 6 5