Return inside loops in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code with return inside a loop?

Look at this Go function. What will it print when called?

Go

package main
import "fmt"

func findFirstEven(nums []int) int {
    for _, n := range nums {
        if n%2 == 0 {
            return n
        }
    }
    return -1
}

func main() {
    fmt.Println(findFirstEven([]int{1, 3, 5, 6, 8}))
}

A -1

B 6

C 0

D 8

💡 Hint

Remember, return exits the function immediately.

The function returns the first even number it finds. It checks 1, 3, 5 (odd), then 6 (even), so it returns 6 immediately.

❓ Predict Output

intermediate

What does this Go function return?

What value does this function return when called with []int{7, 9, 11}?

Go

func findFirstEven(nums []int) int {
    for _, n := range nums {
        if n%2 == 0 {
            return n
        }
    }
    return -1
}

A 11

B 0

C 7

D -1

💡 Hint

If no even number is found, what does the function return?

Since none of the numbers are even, the loop finishes without returning, so the function returns -1.

🔧 Debug

advanced

Why does this Go function always return 0?

Look at this function. It is supposed to return the first even number from the slice, but it always returns 0. Why?

Go

func findFirstEven(nums []int) int {
    for i := 0; i < len(nums); i++ {
        if nums[i]%2 == 0 {
            break
        }
    }
    return 0
}

A The function returns inside the loop, so it exits too early.

B The loop condition is wrong and never runs.

C The function uses break instead of return, so it never returns the even number found.

D The function returns -1 instead of 0.

💡 Hint

What does break do inside a loop?

break exits the loop but the function continues and returns 0 always. To return the even number, return must be used inside the loop.

📝 Syntax

advanced

Which option causes a compile error in Go?

Which of these code snippets will cause a compile error due to incorrect use of return inside a loop?

A

func findFirstEven(nums []int) int {
    for _, n := range nums {
        if n%2 == 0 {
            return n
        }
    }
}

B

1- nruter
}
}    
n nruter        
{ 0 == 2%n fi    
{ smun egnar =: n ,_ rof

C

for _, n := range nums {
    if n%2 == 0 {
        return n
    }
}
return -1

D

for i := 0; i < len(nums); i++ {
    if nums[i]%2 == 0 {
        return nums[i]
    }
}
return -1

💡 Hint

Check if the function always returns a value on all paths.

Option A lacks a return statement after the loop, so if no even number is found, the function has no return value, causing a compile error.

🚀 Application

expert

What is the output of this Go program with nested loops and return?

What will this Go program print?

Go

package main
import "fmt"

func findPair(nums []int, target int) (int, int) {
    for i := 0; i < len(nums); i++ {
        for j := i + 1; j < len(nums); j++ {
            if nums[i]+nums[j] == target {
                return nums[i], nums[j]
            }
        }
    }
    return -1, -1
}

func main() {
    a, b := findPair([]int{1, 3, 5, 7, 9}, 12)
    fmt.Println(a, b)
}

A 3 9

B 5 7

C -1 -1

D 1 11

💡 Hint

The function returns the first pair that sums to the target.

The pairs checked in order are (1,3)=4, (1,5)=6, (1,7)=8, (1,9)=10, (3,5)=8, (3,7)=10, (3,9)=12. The first pair summing to 12 is (3,9), so the function returns 3 and 9 immediately.