30 Kotlin Basic Exercises for Advanced with Solutions
Master advanced Kotlin skills with our comprehensive list of top 30 exercises. Dive into coding challenges that improve your understanding and proficiency in Kotlin, setting a solid foundation for professional-level challenges. Start your journey to Kotlin mastery today!
Learning Objectives:
Master advanced Kotlin features like coroutines, DSLs, generics, and extension functions for scalable development. Design robust, asynchronous, and reactive systems suited for enterprise and Android development.
Exercise Instructions:
- Start with the first exercise and attempt to solve it before checking the hint or solution.
- Ensure you understand the logic behind each solution, as this will help you in more complex problems.
- Use these exercises to reinforce your learning and identify areas that may require further study.
1. Write a function to find the intersection of three arrays.
Required Input:
Write a function to find the intersection of three arrays.Expected Output:
Intersection: [3]
Code In Kotlin
fun intersection(arr1: Array<Int>, arr2: Array<Int>, arr3: Array<Int>): List<Int> {
return arr1.filter { it in arr2 && it in arr3 }
}
fun main() {
val arr1 = arrayOf(1, 2, 3)
val arr2 = arrayOf(2, 3, 4)
val arr3 = arrayOf(3, 4, 5)
println("Intersection: ${intersection(arr1, arr2, arr3)}")
}
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2. Implement a function to calculate the nth Fibonacci number iteratively.
Required Input:
A hardcoded integer, e.g., n = 7.Expected Output:
The 7-th Fibonacci number is: 13
Code In Kotlin
fun fibonacci(n: Int): Int {
if (n <= 1) return n
var a = 0
var b = 1
for (i in 2..n) {
val temp = b
b += a
a = temp
}
return b
}
fun main() {
val n = 7
println("The $n-th Fibonacci number is: ${fibonacci(n)}")
}
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3. Write a function to check if a string is a valid palindrome ignoring spaces.
Required Input:
A hardcoded string, e.g., "A man a plan a canal Panama".Expected Output:
The string is a palindrome
Code In Kotlin
fun isValidPalindrome(input: String): Boolean {
val cleaned = input.replace(" ", "").lowercase()
return cleaned == cleaned.reversed()
}
fun main() {
val input = "A man a plan a canal Panama"
if (isValidPalindrome(input)) {
println("The string is a palindrome")
} else {
println("The string is not a palindrome")
}
}
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4. Create a program to rotate a matrix by 90 degrees clockwise.
Required Input:
A hardcoded matrix, e.g., [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ]Expected Output:
7 4 1
8 5 2
9 6 3
Code In Kotlin
fun rotateMatrix(matrix: Array<Array<Int>>): Array<Array<Int>> {
val n = matrix.size
val rotated = Array(n) { Array(n) { 0 } }
for (i in 0 until n) {
for (j in 0 until n) {
rotated[j][n - i - 1] = matrix[i][j]
}
}
return rotated
}
fun main() {
val matrix = arrayOf(
arrayOf(1, 2, 3),
arrayOf(4, 5, 6),
arrayOf(7, 8, 9)
)
val rotated = rotateMatrix(matrix)
rotated.forEach { println(it.joinToString(" ")) }
}
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5. Write a function to count unique characters in a string.
Required Input:
A hardcoded string, e.g., "programming".Expected Output:
Number of unique characters: 8
Code In Kotlin
fun countUniqueCharacters(input: String): Int {
return input.toSet().size
}
fun main() {
val input = "programming"
println("Number of unique characters: ${countUniqueCharacters(input)}")
}
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6. Implement a function to check if two strings are isomorphic.
Required Input:
Two hardcoded strings, e.g., "egg" and "add".Expected Output:
The strings are isomorphic
Code In Kotlin
fun areIsomorphic(str1: String, str2: String): Boolean {
if (str1.length != str2.length) return false
val map1 = mutableMapOf<Char, Char>()
val map2 = mutableMapOf<Char, Char>()
for (i in str1.indices) {
val c1 = str1[i]
val c2 = str2[i]
if (map1[c1] != null && map1[c1] != c2
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7. Write a function to merge two sorted arrays into a single sorted array without duplicates.
Required Input:
Two hardcoded arrays, e.g., [1, 3, 5] and [2, 3, 6].Expected Output:
Merged array: [1, 2, 3, 5, 6]
Code In Kotlin
fun mergeAndRemoveDuplicates(arr1: Array<Int>, arr2: Array<Int>): List<Int> {
return (arr1 + arr2).toSet().sorted()
}
fun main() {
val arr1 = arrayOf(1, 3, 5)
val arr2 = arrayOf(2, 3, 6)
println("Merged array: ${mergeAndRemoveDuplicates(arr1, arr2)}")
}
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8. Create a program to calculate the greatest common divisor (GCD) of an array of integers.
Required Input:
A hardcoded array of integers, e.g., [12, 15, 18].Expected Output:
GCD of the array: 3
Code In Kotlin
fun gcd(a: Int, b: Int): Int {
return if (b == 0) a else gcd(b, a % b)
}
fun gcdOfArray(arr: Array<Int>): Int {
return arr.reduce { acc, num -> gcd(acc, num) }
}
fun main() {
val arr = arrayOf(12, 15, 18)
println("GCD of the array: ${gcdOfArray(arr)}")
}
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9. Write a function to find the top k frequent elements in an array.
Required Input:
A hardcoded array of integers and an integer k, e.g., [1, 1, 1, 2, 2, 3] and k = 2.Expected Output:
Top 2 frequent elements: [1, 2]
Code In Kotlin
fun topKFrequent(nums: Array<Int>, k: Int): List<Int> {
val frequencyMap = nums.groupingBy { it }.eachCount()
return frequencyMap.entries.sortedByDescending { it.value }.take(k).map { it.key }
}
fun main() {
val nums = arrayOf(1, 1, 1, 2, 2, 3)
val k = 2
println("Top $k frequent elements: ${topKFrequent(nums, k)}")
}
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10. Write a function to find duplicate elements in an array.
Required Input:
A hardcoded array of integers, e.g., [1, 2, 3, 2, 4, 5, 3].Expected Output:
Duplicate elements: [2, 3]
Code In Kotlin
fun findDuplicates(nums: Array<Int>): List<Int> {
val seen = mutableSetOf<Int>()
val duplicates = mutableSetOf<Int>()
for (num in nums) {
if (!seen.add(num)) {
duplicates.add(num)
}
}
return duplicates.toList()
}
fun main() {
val nums = arrayOf(1, 2, 3, 2, 4, 5, 3)
println("Duplicate elements: ${findDuplicates(nums)}")
}
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