Common pointer use cases in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pointer dereference and modification

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 20

B 10

C Compilation error

D Runtime panic

💡 Hint

Remember that modifying the value through a pointer changes the original variable.

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

❓ Predict Output

intermediate

Pointer nil check and output

What will this Go program print?

Go

package main
import "fmt"
func main() {
    var p *int
    if p == nil {
        fmt.Println("Pointer is nil")
    } else {
        fmt.Println("Pointer is not nil")
    }
}

A Runtime panic

B Pointer is nil

C Compilation error

D Pointer is not nil

💡 Hint

Uninitialized pointers have a zero value of nil.

The pointer p is declared but not assigned, so it is nil. The if condition is true, printing "Pointer is nil".

❓ Predict Output

advanced

Effect of pointer on function argument

What is the output of this Go program?

Go

package main
import "fmt"
func increment(n *int) {
    *n = *n + 1
}
func main() {
    x := 5
    increment(&x)
    fmt.Println(x)
}

A 5

B Compilation error

C 6

D Runtime panic

💡 Hint

Passing a pointer allows the function to modify the original variable.

The function increment receives a pointer to x and increases the value it points to by 1. So x becomes 6.

❓ Predict Output

advanced

Pointer to struct field modification

What will this Go program print?

Go

package main
import "fmt"
type Person struct {
    age int
}
func main() {
    p := Person{age: 30}
    ptr := &p.age
    *ptr = 40
    fmt.Println(p.age)
}

A 40

B Runtime panic

C Compilation error

D 30

💡 Hint

Pointers can point to struct fields and modify them directly.

ptr points to p.age. Changing *ptr changes p.age to 40. So printing p.age outputs 40.

🧠 Conceptual

expert

Pointer zero value and memory safety

Which statement about pointers in Go is TRUE?

A Pointers in Go can be used to access private fields of other packages.

B A pointer variable always points to a valid memory address after declaration.

C Go allows pointer arithmetic similar to C.

D Dereferencing a nil pointer causes a runtime panic.

💡 Hint

Think about what happens if you try to use a pointer that has not been assigned.

In Go, a pointer declared but not assigned is nil. Dereferencing nil causes a runtime panic. Go does not support pointer arithmetic and enforces package privacy.