Address and dereference operators in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pointer dereference after assignment

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    x := 10
    p := &x
    *p = 20
    fmt.Println(x)
}

A Compilation error

B 10

C 0

D 20

💡 Hint

Remember that *p changes the value at the address p points to.

The pointer p points to x. Changing *p changes x's value to 20. So printing x outputs 20.

❓ Predict Output

intermediate

Value of variable after pointer reassignment

What will be printed by this Go code?

Go

package main
import "fmt"
func main() {
    a := 5
    b := 10
    p := &a
    p = &b
    *p = 15
    fmt.Println(a, b)
}

A 5 15

B 5 10

C 15 10

D Compilation error

💡 Hint

Pointer p is first set to a, then to b. Changing *p affects which variable?

Initially p points to a, then it points to b. Changing *p = 15 changes b to 15. a remains 5.

🔧 Debug

advanced

Identify the error in pointer usage

What error does this Go code produce?

Go

package main
func main() {
    var p *int
    *p = 10
}

A No error, program prints 10

B Compilation error: cannot assign to *p

C runtime error: invalid memory address or nil pointer dereference

D Compilation error: missing variable declaration

💡 Hint

p is declared but not initialized to point to valid memory.

p is a nil pointer. Dereferencing it (*p) causes a runtime panic due to invalid memory access.

🧠 Conceptual

advanced

Effect of pointer on function argument

What will be the output of this Go program?

Go

package main
import "fmt"
func increment(n *int) {
    *n = *n + 1
}
func main() {
    x := 7
    increment(&x)
    fmt.Println(x)
}

A 7

B 8

C 0

D Compilation error: cannot use &x

💡 Hint

The function changes the value at the address passed.

increment receives a pointer to x and increases the value at that address by 1, so x becomes 8.

❓ Predict Output

expert

Pointer arithmetic and dereference behavior

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    arr := [3]int{1, 2, 3}
    p := &arr[0]
    fmt.Println(*p)
    p = &arr[1]
    fmt.Println(*p)
    p++
    fmt.Println(*p)
}

A Compilation error: invalid operation p++

B

1
2
Compilation error

C

1
2
0

D

1
2
3

💡 Hint

Go does not support pointer arithmetic like p++.

In Go, you cannot increment pointers with ++. This causes a compilation error.