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Learning path

Learn Kotlin step by step

40 challenges in 8 modules take you from variables and conditions to functions, grids and recursion. Solve them in order in Kotlin; each one runs in your browser with instant tests and an AI review.

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  1. 1

    Variables & arithmetic

    Store values, do math with them and return results.

    0/5
    1. 1 Rectangle Perimeter Easy Solve in Kotlin
    2. 2 Celsius to Fahrenheit Easy Solve in Kotlin
    3. 3 Simple Interest Easy Solve in Kotlin
    4. 4 Body Mass Index Easy Solve in Kotlin
    5. 5 Average of Three Easy Solve in Kotlin
  2. 2

    Conditions

    Make decisions with if, else and comparisons.

    0/5
    1. 1 Letter Grade Easy Solve in Kotlin
    2. 2 Largest of Three Easy Solve in Kotlin
    3. 3 Ticket Price by Age Easy Solve in Kotlin
    4. 4 Point Quadrant Easy Solve in Kotlin
    5. 5 Absolute Value Without abs Easy Solve in Kotlin
  3. 3

    Loops

    Repeat work with for and while loops.

    0/5
    1. 1 Sum of Odd Numbers Easy Solve in Kotlin
    2. 2 Multiplication Table Row Easy Solve in Kotlin
    3. 3 Countdown to Liftoff Easy Solve in Kotlin
    4. 4 Power by Repeated Multiplication Easy Solve in Kotlin
    5. 5 Halve Until One Easy Solve in Kotlin
  4. 4

    Nested loops & patterns

    Put loops inside loops to build tables and shapes.

    0/5
    1. 1 Pyramid Rows Easy Solve in Kotlin
    2. 2 Multiplication Grid Easy Solve in Kotlin
    3. 3 Count Pairs With a Sum Easy Solve in Kotlin
    4. 4 Number Triangle Easy Solve in Kotlin
    5. 5 Hollow Square Easy Solve in Kotlin
  5. 5

    Strings

    Read, build and transform text character by character.

    0/5
    1. 1 Count Uppercase Letters Easy Solve in Kotlin
    2. 2 Initials From a Name Easy Solve in Kotlin
    3. 3 Every Other Character Easy Solve in Kotlin
    4. 4 Replace Spaces With Dashes Easy Solve in Kotlin
    5. 5 Password Rules Check Easy Solve in Kotlin
  6. 6

    Lists

    Work with collections of values: count, filter and transform.

    0/5
    1. 1 Count Positive Numbers Easy Solve in Kotlin
    2. 2 Running Sum Easy Solve in Kotlin
    3. 3 Above-Average Values Easy Solve in Kotlin
    4. 4 Swap First and Last Easy Solve in Kotlin
    5. 5 First Negative Index Easy Solve in Kotlin
  7. 7

    Functions

    Split a problem into small reusable functions.

    0/5
    1. 1 Days in a Month Easy Solve in Kotlin
    2. 2 Distance Between Points Easy Solve in Kotlin
    3. 3 Cart Total With Discount Easy Solve in Kotlin
    4. 4 Min and Max Together Easy Solve in Kotlin
    5. 5 Gradebook Top Student Medium Solve in Kotlin
  8. 8

    Grids & recursion

    Walk 2D grids and solve problems that call themselves.

    0/5
    1. 1 Row Sums Easy Solve in Kotlin
    2. 2 Tic-Tac-Toe Winner Medium Solve in Kotlin
    3. 3 Recursive Power Medium Solve in Kotlin
    4. 4 Recursive Palindrome Medium Solve in Kotlin
    5. 5 Count Islands Medium Solve in Kotlin