Operator precedence in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code involving mixed operators?

Consider the following Kotlin code snippet:

val result = 3 + 4 * 2 / (1 - 5) % 2
println(result)

What will be printed?

Kotlin

val result = 3 + 4 * 2 / (1 - 5) % 2
println(result)

A 2

B 1

C 0

D 3

💡 Hint

Remember the order: parentheses, multiplication/division/modulus, then addition/subtraction.

First, (1 - 5) = -4.
Then, 4 * 2 = 8.
Next, 8 / -4 = -2.
Then, -2 % 2 = 0 (because -2 mod 2 is 0 in Kotlin).
Finally, 3 + 0 = 3.

❓ Predict Output

intermediate

What is the value of x after this Kotlin expression?

Given this Kotlin code:

var x = 10
x += 3 * 2 - 4 / 2

What is the value of x after running this?

Kotlin

var x = 10
x += 3 * 2 - 4 / 2
println(x)

A 15

B 16

C 14

D 17

💡 Hint

Calculate multiplication and division before addition and subtraction.

3 * 2 = 6
4 / 2 = 2
Then 6 - 2 = 4
x += 4 means x = 10 + 4 = 14

❓ Predict Output

advanced

What does this Kotlin code print with logical and arithmetic operators?

Analyze this Kotlin code:

val a = true
val b = false
val c = 5
val d = 10
val result = a && b || c < d && !b
println(result)

What is the output?

Kotlin

val a = true
val b = false
val c = 5
val d = 10
val result = a && b || c < d && !b
println(result)

A false

B true

C Compilation error

D Runtime exception

💡 Hint

Remember that && has higher precedence than ||, and ! has highest precedence.

!b = !false = true
a && b = true && false = false
c < d = 5 < 10 = true
c < d && !b = true && true = true
Then false || true = true

❓ Predict Output

advanced

What is the output of this Kotlin code with mixed increment and arithmetic?

Consider this Kotlin snippet:

var x = 5
val y = x++ * 2 + --x
println(y)

What will be printed?

Kotlin

var x = 5
val y = x++ * 2 + --x
println(y)

A 15

B 23

C 29

D 25

💡 Hint

Remember post-increment returns the value before increment, pre-decrement decrements before use.

Initial x=5
x++ returns 5, then x becomes 6
--x decrements x to 5, then returns 5
So y = 5 * 2 + 5 = 10 + 5 = 15

❓ Predict Output

expert

What is the output of this Kotlin code with chained assignments and operator precedence?

Analyze this Kotlin code:

var a = 2
var b = 3
var c = 4
val result = a + b * c / a - b % c
println(result)

What will be printed?

Kotlin

var a = 2
var b = 3
var c = 4
val result = a + b * c / a - b % c
println(result)

A 5

B 7

C 6

D 4

💡 Hint

Follow operator precedence: multiplication/division/modulus before addition/subtraction.

b * c = 3 * 4 = 12
12 / a = 12 / 2 = 6
b % c = 3 % 4 = 3
Then a + 6 - 3 = 2 + 6 - 3 = 5

Practice

1. In Kotlin, which operator has the highest precedence in the expression 3 + 4 * 2?

easy

A. Multiplication (*)

B. Addition (+)

C. Subtraction (-)

D. Division (/)

Solution

1. Step 1: Identify operators in the expression

   The expression has addition (+) and multiplication (*).

2. Step 2: Recall operator precedence rules

   Multiplication (*) has higher precedence than addition (+), so it runs first.

3. Final Answer:

   Multiplication (*) -> Option A

4. Quick Check:

   Multiplication before addition = Multiplication (*) [OK]

Hint: Multiply and divide before adding or subtracting [OK]

Common Mistakes:

• Thinking addition runs before multiplication
• Ignoring operator precedence
• Assuming left to right always applies

2. Which of the following Kotlin expressions correctly uses parentheses to change the order of operations in 3 + 4 * 2 so that addition happens first?

easy

A. 3 + (4 * 2)

B. (3 + 4) * 2

C. 3 + 4 * 2

D. 3 * (4 + 2)

Solution

1. Step 1: Understand default precedence

   Without parentheses, multiplication runs before addition.

2. Step 2: Check which option forces addition first

   (3 + 4) * 2 uses parentheses around (3 + 4), so addition happens before multiplication.

3. Final Answer:

   (3 + 4) * 2 -> Option B

4. Quick Check:

   Parentheses change order = (3 + 4) * 2 [OK]

Hint: Use parentheses to force addition before multiplication [OK]

Common Mistakes:

• Ignoring parentheses effect
• Choosing expression without parentheses
• Assuming left to right overrides precedence

3. What is the output of this Kotlin code?

val result = 10 - 4 + 2 * 3
println(result)

medium

A. 12

B. 18

C. 14

D. 4

Solution

1. Step 1: Apply operator precedence

   Multiplication (*) runs first: 2 * 3 = 6.

2. Step 2: Evaluate remaining expression left to right

   10 - 4 + 6 = 6 + 6 = 12.

3. Final Answer:

   12 -> Option A

4. Quick Check:

   Multiplication before addition/subtraction = 12 [OK]

Hint: Multiply before adding or subtracting [OK]

Common Mistakes:

• Adding before multiplying
• Calculating left to right ignoring precedence
• Miscomputing subtraction and addition order

4. Find the error in this Kotlin expression:

val x = 5 + 3 * 2 && true

What is the problem?

medium

A. Logical AND (&&) has higher precedence than multiplication

B. Missing semicolon at the end

C. Multiplication operator is invalid here

D. Cannot mix arithmetic and boolean operators without parentheses

Solution

1. Step 1: Identify mixed types in expression

   The expression mixes arithmetic (5 + 3 * 2) and boolean (&& true) without separation.

2. Step 2: Understand Kotlin type rules

   You cannot combine Int and Boolean directly without explicit logic or parentheses.

3. Final Answer:

   Cannot mix arithmetic and boolean operators without parentheses -> Option D

4. Quick Check:

   Mixing Int and Boolean needs care [OK]

Hint: Don't mix numbers and booleans without clear separation [OK]

Common Mistakes:

• Thinking semicolon is missing
• Assuming && works with numbers
• Ignoring type mismatch errors

5. Given the Kotlin expression:

val result = true || false && false || true && false

What is the value of result considering operator precedence?

hard

A. false

B. Syntax error

C. true

D. null

Solution

1. Step 1: Recall logical operator precedence

   Logical AND (&&) has higher precedence than OR (||), so evaluate && first.

2. Step 2: Evaluate all AND operations

   false && false = false, true && false = false.

3. Step 3: Replace and evaluate OR operations left to right

   true || false || false = true || false = true.

4. Final Answer:

   true -> Option C

5. Quick Check:

   AND before OR, final result true [OK]

Hint: Evaluate && before || in logical expressions [OK]

Common Mistakes:

• Evaluating OR before AND
• Confusing operator precedence
• Assuming expression returns null or error