Enum with properties and methods in Kotlin - Time & Space Complexity

Time Complexity: Enum with properties and methods

O(n)

Understanding Time Complexity

Enums with properties and methods let us group related values with extra details and actions.

We want to see how the time to run code with enums changes as we use more enum values or call their methods.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

enum class Color(val rgb: Int) {
    RED(0xFF0000) {
        override fun printName() = println("Red")
    },
    GREEN(0x00FF00) {
        override fun printName() = println("Green")
    },
    BLUE(0x0000FF) {
        override fun printName() = println("Blue")
    };

    abstract fun printName()
}

fun printAllColors() {
    for (color in Color.values()) {
        color.printName()
    }
}

This code defines an enum with three colors, each having a property and a method. Then it loops over all colors and calls their method.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Looping over all enum values with Color.values() and calling printName().
• How many times: Once for each enum constant (3 times here, but can be more if enum grows).

How Execution Grows With Input

As the number of enum constants grows, the loop runs once per constant.

Input Size (n)	Approx. Operations
3	3 calls to printName()
10	10 calls to printName()
100	100 calls to printName()

Pattern observation: The work grows directly with the number of enum values. More values mean more method calls.

Final Time Complexity

Time Complexity: O(n)

This means the time to run the loop and call methods grows linearly with the number of enum constants.

Common Mistake

[X] Wrong: "Enums are fixed and small, so their methods always run in constant time no matter what."

[OK] Correct: While enums often have few values, if you loop over all values or add many constants, the time grows with the number of constants, not always constant.

Interview Connect

Understanding how enum methods run helps you explain how your code scales when using enums with many values or complex methods.

Self-Check

"What if the printName() method called another function that loops over a list inside each enum constant? How would the time complexity change?"

Practice

1. What is the main purpose of using an enum with properties and methods in Kotlin?

easy

A. To group related fixed values with additional data and behavior

B. To create a list of unrelated variables

C. To define functions without any fixed values

D. To replace all classes in Kotlin

Solution

1. Step 1: Understand enum basics

   Enums group fixed related values, like days or colors.

2. Step 2: Recognize added properties and methods

   Adding properties and methods lets each enum value hold extra data and behavior.

3. Final Answer:

   To group related fixed values with additional data and behavior -> Option A

4. Quick Check:

   Enums = fixed values + extra data [OK]

Hint: Enums bundle fixed options with data and actions [OK]

Common Mistakes:

• Thinking enums are for unrelated variables
• Confusing enums with regular classes
• Assuming enums can't have methods

2. Which of the following is the correct syntax to declare an enum with a property color of type String in Kotlin?

easy

A. enum class Fruit { APPLE(color = "Red"), BANANA(color = "Yellow") }

B. enum Fruit { APPLE: String = "Red", BANANA: String = "Yellow" }

C. enum class Fruit(val color: String) { APPLE("Red"), BANANA("Yellow") }

D. enum class Fruit { val color: String = "Red"; APPLE, BANANA }

Solution

1. Step 1: Check enum class declaration with property

   In Kotlin, enum classes can have constructor parameters like val color: String.

2. Step 2: Verify enum values initialization

   Each enum value must pass the property value in parentheses, e.g., APPLE("Red").

3. Final Answer:

   enum class Fruit(val color: String) { APPLE("Red"), BANANA("Yellow") } -> Option C

4. Quick Check:

   Enum with constructor and values = enum class Fruit(val color: String) { APPLE("Red"), BANANA("Yellow") } [OK]

Hint: Use constructor parameters and pass values in parentheses [OK]

Common Mistakes:

• Using colon syntax instead of constructor parameters
• Trying to assign properties inside enum body incorrectly
• Omitting parentheses for enum values

3. What will be the output of the following Kotlin code?

enum class Size(val label: String) {
    SMALL("S"), MEDIUM("M"), LARGE("L");
    fun description() = "Size is $label"
}

fun main() {
    println(Size.MEDIUM.description())
}

medium

A. Size is M

B. Size is MEDIUM

C. MEDIUM

D. Size.MEDIUM

Solution

1. Step 1: Understand enum property and method

   Each enum value has a label property: MEDIUM has "M".

2. Step 2: Evaluate the description() method call

   The method returns "Size is $label", so for MEDIUM it returns "Size is M".

3. Final Answer:

   Size is M -> Option A

4. Quick Check:

   Method uses label property = "Size is M" [OK]

Hint: Method uses property value, not enum name [OK]

Common Mistakes:

• Printing enum name instead of property
• Confusing property label with enum constant name
• Ignoring method call output

4. Identify the error in this Kotlin enum declaration:

enum class Direction(val degrees: Int) {
    NORTH(0),
    EAST(90),
    SOUTH(180),
    WEST
}

medium

A. Semicolon missing after enum constants

B. Cannot have properties in enum classes

C. Enum constants must be lowercase

D. Missing property value for WEST enum constant

Solution

1. Step 1: Check enum constructor parameters

   The enum class requires an Int parameter degrees for each constant.

2. Step 2: Verify each enum constant initialization

   All constants except WEST provide a value; WEST is missing (value).

3. Final Answer:

   Missing property value for WEST enum constant -> Option D

4. Quick Check:

   All enum constants must pass constructor values [OK]

Hint: All enum constants must provide constructor arguments [OK]

Common Mistakes:

• Forgetting to pass constructor arguments for all constants
• Assuming semicolon is mandatory after constants
• Thinking enum constants must be lowercase

5. Given this enum with a method:

enum class TrafficLight(val duration: Int) {
    RED(30) {
        override fun signal() = "Stop"
    },
    YELLOW(5) {
        override fun signal() = "Caution"
    },
    GREEN(25) {
        override fun signal() = "Go"
    };
    abstract fun signal(): String
}

fun main() {
    val lights = TrafficLight.values()
    val signals = lights.map { it.signal() }
    println(signals)
}

What is the output when running main()?

hard

A. [30, 5, 25]

B. ["Stop", "Caution", "Go"]

C. [RED, YELLOW, GREEN]

D. ["Go", "Caution", "Stop"]

Solution

1. Step 1: Understand enum with abstract method

   Each enum constant overrides signal() to return a specific string.

2. Step 2: Map enum values to their signals

   The map calls signal() on each constant, producing ["Stop", "Caution", "Go"].

3. Final Answer:

   ["Stop", "Caution", "Go"] -> Option B

4. Quick Check:

   Abstract method overridden per constant = correct signals [OK]

Hint: Abstract method overridden per enum constant returns correct string [OK]

Common Mistakes:

• Printing enum names instead of method results
• Confusing property values with method outputs
• Ignoring abstract method override requirement