Function declaration in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a function returning multiple values

What is the output of this Go program?

Go

package main
import "fmt"

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

func main() {
    q, r := divideAndRemainder(17, 5)
    fmt.Println(q, r)
}

A 3 1

B 4 2

C 3 2

D Error: multiple return values not handled

💡 Hint

Remember that 17 divided by 5 is 3 with remainder 2.

The function divides 17 by 5 returning quotient 3 and remainder 2. The main function prints these values.

❓ Predict Output

intermediate

Output of a function with named return values

What does this Go program print?

Go

package main
import "fmt"

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

func main() {
    a, b := swap("hello", "world")
    fmt.Println(a, b)
}

A world world

B hello world

C hello hello

D world hello

💡 Hint

Named return values are assigned inside the function before return.

The function swaps the two strings by assigning named return variables and returns them. So output is 'world hello'.

❓ Predict Output

advanced

Output of recursive function calculating factorial

What is the output of this Go program?

Go

package main
import "fmt"

func factorial(n int) int {
    if n <= 1 {
        return 1
    }
    return n * factorial(n-1)
}

func main() {
    fmt.Println(factorial(5))
}

A 120

B 24

C Error: stack overflow

D 5

💡 Hint

Factorial of 5 is 5*4*3*2*1.

The recursive function correctly calculates factorial by multiplying n by factorial of n-1 until base case 1.

❓ Predict Output

advanced

Output of function with variadic parameters

What does this Go program print?

Go

package main
import "fmt"

func sum(nums ...int) int {
    total := 0
    for _, n := range nums {
        total += n
    }
    return total
}

func main() {
    fmt.Println(sum(1, 2, 3, 4))
}

A 10

B 24

C Error: cannot use ... with int

D 0

💡 Hint

Sum all numbers passed as arguments.

The variadic function sums all integers passed and returns the total 10.

❓ Predict Output

expert

Output of function returning a closure capturing variable

What is the output of this Go program?

Go

package main
import "fmt"

func makeCounter() func() int {
    count := 0
    return func() int {
        count++
        return count
    }
}

func main() {
    counter := makeCounter()
    fmt.Println(counter())
    fmt.Println(counter())
    fmt.Println(counter())
}

A Error: cannot return closure

B

1
2
3

C

1
1
1

D

0
1
2

💡 Hint

Closures remember the variable state between calls.

The returned function increments and returns count each time, producing 1, 2, 3.