Common slice operations in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this slice append operation?

Consider the following Go code snippet. What will be printed?

Go

package main
import "fmt"
func main() {
    s := []int{1, 2, 3}
    s = append(s, 4, 5)
    fmt.Println(s)
}

A [4 5]

B [1 2 3]

C [1 2 3 4 5]

D Compilation error

💡 Hint

Remember that append adds elements to the end of the slice.

The append function adds the elements 4 and 5 to the existing slice s, resulting in [1 2 3 4 5].

❓ Predict Output

intermediate

What does this slice slicing produce?

What will be the output of this Go program?

Go

package main
import "fmt"
func main() {
    s := []string{"a", "b", "c", "d", "e"}
    fmt.Println(s[1:4])
}

A runtime error: index out of range

B ["a" "b" "c"]

C ["c" "d" "e"]

D ["b" "c" "d"]

💡 Hint

Remember slice[start:end] includes start but excludes end.

The slice s[1:4] includes elements at indices 1, 2, and 3, which are "b", "c", and "d".

❓ Predict Output

advanced

What is the output of this slice capacity and length code?

What will this Go program print?

Go

package main
import "fmt"
func main() {
    s := make([]int, 3, 5)
    fmt.Println(len(s), cap(s))
    s = s[:5]
    fmt.Println(len(s), cap(s))
}

A

3 5
3 5

B

3 5
5 5

C

3 3
5 5

D runtime error: slice bounds out of range

💡 Hint

Length is the number of elements, capacity is the underlying array size.

Initially, length is 3 and capacity is 5. Extending the slice to length 5 is valid and updates length to 5 while capacity stays 5.

❓ Predict Output

advanced

What happens when you remove an element from a slice?

What will be printed by this Go program?

Go

package main
import "fmt"
func main() {
    s := []int{10, 20, 30, 40, 50}
    i := 2
    s = append(s[:i], s[i+1:]...)
    fmt.Println(s)
}

A [10 20 40 50]

B runtime error: slice bounds out of range

C [10 20 30 50]

D [10 20 30 40 50]

💡 Hint

Appending slices can be used to remove elements.

The element at index 2 (value 30) is removed by appending the parts before and after it.

🧠 Conceptual

expert

What error does this slice operation cause?

What error will this Go code produce when run?

Go

package main
func main() {
    s := []int{1, 2, 3}
    s = s[:4]
}

A runtime error: slice bounds out of range

B compilation error: invalid slice index

C no error, slice extended with zero values

D panic: index out of range

💡 Hint

You cannot extend a slice beyond its capacity.

Trying to slice beyond the capacity causes a runtime panic with 'slice bounds out of range'.