Trie Node Design and Initialization in DSA Go - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Trie Node Initialization

What is the output of this Go code that initializes a Trie node and prints its children count?

DSA Go

package main

import (
	"fmt"
)

type TrieNode struct {
	children map[rune]*TrieNode
	isEnd    bool
}

func NewTrieNode() *TrieNode {
	return &TrieNode{children: make(map[rune]*TrieNode), isEnd: false}
}

func main() {
	node := NewTrieNode()
	fmt.Println(len(node.children))
}

A 0

B 1

C Compilation error

D nil

💡 Hint

Think about what happens when you create a new map in Go and check its length before adding any elements.

The NewTrieNode function creates a TrieNode with an empty map for children. The length of an empty map is 0, so printing len(node.children) outputs 0.

❓ Predict Output

intermediate

Trie Node isEnd Field Default Value

What is the output of this Go code that creates a Trie node and prints the isEnd field?

DSA Go

package main

import (
	"fmt"
)

type TrieNode struct {
	children map[rune]*TrieNode
	isEnd    bool
}

func NewTrieNode() *TrieNode {
	return &TrieNode{children: make(map[rune]*TrieNode)}
}

func main() {
	node := NewTrieNode()
	fmt.Println(node.isEnd)
}

A 0

B true

C false

D Compilation error

💡 Hint

Boolean fields in Go default to what value if not explicitly set?

In Go, boolean fields default to false if not set. The isEnd field is not set in NewTrieNode, so it prints false.

🔧 Debug

advanced

Identify the Error in Trie Node Initialization

What error does this Go code produce when trying to add a child node to the TrieNode's children map?

DSA Go

package main

import (
	"fmt"
)

type TrieNode struct {
	children map[rune]*TrieNode
	isEnd    bool
}

func main() {
	node := &TrieNode{}
	node.children['a'] = &TrieNode{}
	fmt.Println(len(node.children))
}

A 1

B 0

C Compilation error: invalid map key

D panic: assignment to entry in nil map

💡 Hint

Maps must be initialized before adding keys in Go.

The children map is nil because it was not initialized with make. Assigning to a nil map causes a runtime panic.

❓ Predict Output

advanced

Output After Adding Child to Trie Node

What is the output of this Go code after adding a child node to the TrieNode's children map?

DSA Go

package main

import (
	"fmt"
)

type TrieNode struct {
	children map[rune]*TrieNode
	isEnd    bool
}

func NewTrieNode() *TrieNode {
	return &TrieNode{children: make(map[rune]*TrieNode)}
}

func main() {
	node := NewTrieNode()
	node.children['b'] = NewTrieNode()
	fmt.Println(len(node.children))
}

A 0

B 1

C Compilation error

D panic: assignment to entry in nil map

💡 Hint

Check if the children map is initialized before adding a child.

The children map is initialized with make, so adding a child increases its length to 1.

🧠 Conceptual

expert

Why Initialize Children Map in Trie Node?

Why is it important to initialize the children map in a TrieNode struct in Go before adding child nodes?

A Because maps in Go are nil by default and assigning to a nil map causes a runtime panic

B Because uninitialized maps automatically create keys with zero values

C Because initializing maps improves performance but is not required

D Because Go requires all struct fields to be initialized explicitly

💡 Hint

Think about what happens when you try to write to a nil map in Go.

Maps in Go default to nil. Writing to a nil map causes a runtime panic. Initializing with make creates a usable map.