Kotlin program: Sort integer list in descending order with lambda

Last update on February 04 2025 11:06:44 (UTC/GMT +8 hours)

Write a Kotlin program that implements a lambda expression to sort a list of integers in descending order.

Pre-Knowledge (Before You Start!)

Before solving this exercise, you should be familiar with the following concepts:

• Lambda Expressions: A lambda expression is a short, anonymous function that can be used to perform operations on elements within collections.
• Sorting Lists: The sortedByDescending() function sorts a list based on the criteria defined in the lambda expression, arranging elements from highest to lowest.
• Iteration: The forEach function allows iterating over each element in a collection to perform an action, such as printing each element.

Hints (Try Before Looking at the Solution!)

Here are some hints to help you solve the problem:

• Hint 1: Create a list of integers that you want to sort.
• Hint 2: Use the sortedByDescending() function with a lambda expression to sort the list.
• Hint 3: Inside the lambda, return each element as is to sort by the values themselves.
• Hint 4: Store the sorted list in a variable.
• Hint 5: Use forEach to iterate over the sorted list and print each number on a new line.

Sample Solution:

Kotlin Code:

fun main() {
    val numbers = listOf(10, 2, 7, 4, 1, 5, 8, 9, 3, 6)

    val sortedList = numbers.sortedByDescending { it }

    println("Sorted List in Descending Order:")
    sortedList.forEach { println(it) }
}

Sample Output:

Sorted List in Descending Order:
10
9
8
7
6
5
4
3
2
1

Explanation:

In the above exercise -

• We have a list of integers called "numbers". We use the sortedByDescending function on the numbers list and provide a lambda expression { it } as the sorting criteria.
• Inside the lambda expression, we simply return the element itself (it). This lambda expression tells the sortedByDescending function to sort the list in descending order based on the integer values.
• Finally, we print the sorted list in descending order using println and forEach to iterate over each integer in the sorted list and print it on a separate line.

Kotlin Editor:

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