Multiple return values in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code with multiple return values?

Look at this Go function that returns two values. What will be printed?

Go

package main
import "fmt"

func divide(a, b int) (int, int) {
    return a / b, a % b
}

func main() {
    q, r := divide(10, 3)
    fmt.Println(q, r)
}

A Error: cannot use divide(10, 3) in multiple assignment

B 3 0

C 3 3

D 3 1

💡 Hint

Remember that the first return value is the quotient and the second is the remainder.

The function divides 10 by 3. The quotient is 3 and the remainder is 1, so it prints "3 1".

❓ Predict Output

intermediate

What happens when you ignore one return value in Go?

What will this program print?

Go

package main
import "fmt"

func getValues() (int, string) {
    return 42, "hello"
}

func main() {
    val, _ := getValues()
    fmt.Println(val)
}

A 42

B hello

C Compilation error due to unused variable

D 42 hello

💡 Hint

The underscore (_) is used to ignore a return value.

The second return value is ignored using _, so only 42 is printed.

❓ Predict Output

advanced

What is the output of this Go function returning named values?

Check the named return values and what the function returns.

Go

package main
import "fmt"

func swap(x, y int) (a int, b int) {
    a = y
    b = x
    return
}

func main() {
    a, b := swap(5, 10)
    fmt.Println(a, b)
}

A 5 10

B 10 5

C 0 0

D Compilation error: missing return values

💡 Hint

Named return values can be returned by just using return without arguments.

The function swaps the values by assigning named returns and returns them implicitly, so output is "10 5".

❓ Predict Output

advanced

What error does this Go code produce when returning multiple values?

What error will this code cause?

Go

package main

func foo() (int, int) {
    return 1
}

func main() {}

A syntax error: unexpected newline

B missing return at end of function

C cannot use 1 (type int) as type (int, int) in return statement

D no error, compiles fine

💡 Hint

Check the number of values returned compared to the function signature.

The function expects two return values but only returns one, causing a type mismatch error.

🧠 Conceptual

expert

How many values does this Go function return and what are their types?

Analyze this function signature and tell how many values it returns and their types.

Go

func process(data []int) (sum int, avg float64, err error) {
    // implementation omitted
    return
}

A Three values: int, float64, and error

B Two values: int and float64

C Three values: int, int, and error

D One value: a struct containing int, float64, and error

💡 Hint

Look at the named return values and their types carefully.

The function returns three values: sum (int), avg (float64), and err (error).

Practice

1. In Go, what does it mean when a function returns multiple values?

easy

A. The function sends back more than one result at the same time.

B. The function can only return one value but multiple times.

C. The function returns a list of values inside a slice.

D. The function returns values only if an error occurs.

Solution

1. Step 1: Understand function return types in Go

   Go functions can list multiple types in parentheses to return several values together.

2. Step 2: Interpret multiple return values meaning

   This means the function sends back more than one result at once, not just one or a list.

3. Final Answer:

   The function sends back more than one result at the same time. -> Option A

4. Quick Check:

   Multiple return values = more than one result [OK]

Hint: Multiple return means several results sent together [OK]

Common Mistakes:

• Thinking it returns a slice or array
• Assuming only one value can be returned
• Confusing multiple returns with repeated calls

2. Which of the following is the correct syntax to declare a function in Go that returns two integers?

easy

A. func add() int, int { return 1, 2 }

B. func add() [int, int] { return 1, 2 }

C. func add() { return 1, 2 }

D. func add() (int, int) { return 1, 2 }

Solution

1. Step 1: Check Go function return type syntax

   In Go, multiple return types are enclosed in parentheses like (int, int).

2. Step 2: Match syntax with options

   func add() (int, int) { return 1, 2 } correctly uses (int, int) and returns two integers separated by a comma.

3. Final Answer:

   func add() (int, int) { return 1, 2 } -> Option D

4. Quick Check:

   Multiple returns use parentheses (type1, type2) [OK]

Hint: Use parentheses around multiple return types [OK]

Common Mistakes:

• Omitting parentheses around return types
• Using square brackets instead of parentheses
• Returning multiple values without declaring types

3. What will be the output of this Go program?

package main
import "fmt"
func divide(a, b int) (int, int) {
    return a / b, a % b
}
func main() {
    q, r := divide(10, 3)
    fmt.Println(q, r)
}

medium

A. 3 3

B. 3 0

C. 3 1

D. 10 3

Solution

1. Step 1: Understand the divide function

   The function returns two values: quotient (a / b) and remainder (a % b).

2. Step 2: Calculate divide(10, 3)

   10 divided by 3 is 3 with remainder 1, so returns (3, 1).

3. Final Answer:

   3 1 -> Option C

4. Quick Check:

   10/3=3 remainder 1 [OK]

Hint: Remember / is quotient, % is remainder [OK]

Common Mistakes:

• Confusing remainder with quotient
• Swapping the order of returned values
• Expecting a single return value

4. Identify the error in this Go function that returns two strings:

func names() (string, string) {
    return "Alice"
}

medium

A. Missing second return value causes a compile error.

B. Function should return only one string, not two.

C. Return statement syntax is incorrect.

D. Function must have parameters to return multiple values.

Solution

1. Step 1: Check function return signature

   The function declares it returns two strings (string, string).

2. Step 2: Check return statement

   It returns only one string "Alice", missing the second value, causing a compile error.

3. Final Answer:

   Missing second return value causes a compile error. -> Option A

4. Quick Check:

   Return count must match declared types [OK]

Hint: Return values count must match function signature [OK]

Common Mistakes:

• Returning fewer values than declared
• Assuming parameters affect return count
• Incorrect return statement syntax

5. You want to write a Go function that returns the minimum and maximum values from a slice of integers. Which function correctly returns both values?

hard

A. func minMax(nums []int) int {
min, max := nums[0], nums[0]
for _, v := range nums {
if v < min {
min = v
}
if v > max {
max = v
}
}
return min, max
}

B. func minMax(nums []int) (int, int) {
min, max := nums[0], nums[0]
for _, v := range nums {
if v < min {
min = v
}
if v > max {
max = v
}
}
return min, max
}

C. func minMax(nums []int) (int) {
min, max := nums[0], nums[0]
for _, v := range nums {
if v < min {
min = v
}
if v > max {
max = v
}
}
return min, max
}

D. func minMax(nums []int) (int, int) {
min := nums[0]
max := nums[0]
for i := 1; i < len(nums); i++ {
if nums[i] < min {
min = nums[i]
}
if nums[i] > max {
max = nums[i]
}
}
return max, min
}

Solution

1. Step 1: Check function return types

   Function must return two integers (min and max), so signature must be (int, int).

2. Step 2: Verify logic and return order

   func minMax(nums []int) (int, int) { min, max := nums[0], nums[0] for _, v := range nums { if v < min { min = v } if v > max { max = v } } return min, max } correctly initializes min and max, loops through nums, updates min and max, and returns min, max in correct order.

3. Final Answer:

   func minMax(nums []int) (int, int) { min, max := nums[0], nums[0] for _, v := range nums { if v < min { min = v } if v > max { max = v } } return min, max } -> Option B

4. Quick Check:

   Return (min, max) with correct signature and logic [OK]

Hint: Return multiple values with matching signature and correct order [OK]

Common Mistakes:

• Wrong return type signature
• Returning values in wrong order
• Returning only one value instead of two