Why maps are used in Go - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Purpose of maps in Go

Why do programmers use maps in Go?

A To create graphical user interfaces

B To perform mathematical calculations efficiently

C To store key-value pairs for fast data lookup

D To manage concurrent processes automatically

💡 Hint

Think about how you find a phone number quickly in a phone book.

Maps store data as key-value pairs, allowing quick access to values using keys, similar to looking up a name in a dictionary.

❓ Predict Output

intermediate

Output of map lookup

What is the output of this Go code?

Go

package main
import "fmt"
func main() {
  m := map[string]int{"apple": 5, "banana": 3}
  fmt.Println(m["apple"])
}

A banana

B 0

C apple

D 5

💡 Hint

Look at the value stored for the key "apple".

The map stores 5 for the key "apple", so printing m["apple"] outputs 5.

❓ Predict Output

advanced

Map key existence check

What does this Go code print?

Go

package main
import "fmt"
func main() {
  m := map[string]int{"x": 10}
  val, ok := m["y"]
  fmt.Println(val, ok)
}

A 0 true

B 0 false

C 10 false

D 10 true

💡 Hint

Check if the key "y" exists in the map.

The key "y" is not in the map, so val is zero value 0 and ok is false.

🔧 Debug

advanced

Why does this map assignment cause a panic?

What causes the panic in this Go code?

Go

package main
func main() {
  var m map[string]int
  m["key"] = 1
}

A The map is nil and not initialized before assignment

B The key "key" is invalid for map assignment

C The map type is incorrect for string keys

D The map must be declared with make inside main

💡 Hint

Maps must be created before use.

Declaring a map variable without initializing it results in a nil map. Assigning to a nil map causes a runtime panic.

🧠 Conceptual

expert

Why maps are preferred over slices for lookups

Why is a map preferred over a slice when you need to find an item by a key quickly?

A Maps provide constant time lookup, slices require scanning all elements

B Slices use less memory than maps for large data

C Maps keep elements in order, slices do not

D Slices automatically sort elements, maps do not

💡 Hint

Think about how fast you can find a word in a dictionary versus a list.

Maps use hashing to find keys quickly in constant time, while slices require checking each element until the key is found.