Why Trie Exists and What Hash Map Cannot Do for Strings in DSA Go - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a word into the Trie.

DSA Go

func (t *TrieNode) Insert(word string) {
    node := t
    for _, ch := range word {
        if node.children[ch] == nil {
            node.children[ch] = &TrieNode{children: make(map[rune]*TrieNode)}
        }
        node = node.children[[1]]
    }
    node.isEnd = true
}

Drag options to blanks, or click blank then click option'

Ach

Bword

Cnode

Dt

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole word instead of a single character as key.

Using the wrong variable like node or t instead of ch.

The loop iterates over each character ch in the word. We use ch as the key to access or create the child node in the Trie.

2fill in blank

medium

Complete the code to check if a word exists in the Trie.

DSA Go

func (t *TrieNode) Search(word string) bool {
    node := t
    for _, ch := range word {
        if node.children[[1]] == nil {
            return false
        }
        node = node.children[ch]
    }
    return node.isEnd
}

Drag options to blanks, or click blank then click option'

Aword

Bnode

Cch

Dt

Attempts:

3 left

💡 Hint

Common Mistakes

Checking with the whole word instead of character.

Using wrong variable as key.

We check if the child node for the current character ch exists. If not, the word is not in the Trie.

3fill in blank

hard

Fix the error in the code to find if any word starts with the given prefix.

DSA Go

func (t *TrieNode) StartsWith(prefix string) bool {
    node := t
    for _, ch := range prefix {
        if node.children[ch] == nil {
            return false
        }
        node = node.children[[1]]
    }
    return true
}

Drag options to blanks, or click blank then click option'

Ach

Bnode

Cprefix

Dt

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole prefix string instead of character.

Using wrong variable like node or t.

We must use the current character ch to move to the next child node while checking the prefix.

4fill in blank

hard

Fill both blanks to create a map comprehension that counts characters in a string.

DSA Go

counts := map[rune]int{}
for _, ch := range word {
    counts[ch] [1] 1
}
result := map[rune]int{ch: counts[ch] [2] 0 for ch := range counts}

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A+=

B-=

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using -= instead of += for counting.

Using - instead of + when copying counts.

We increment the count for each character using += 1. Then we create a new map with counts added to zero using + 0 to copy values.

5fill in blank

hard

Fill all three blanks to create a filtered map of characters with counts greater than zero.

DSA Go

filtered := map[rune]int{ch: counts[ch] for ch := range counts if counts[ch] [1] 0 && ch [2] 'a' && ch [3] '{' }

Drag options to blanks, or click blank then click option'

A>

B==

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of > for counts.

Using wrong comparison operators for character range.

We filter characters with counts greater than zero (>), and characters between 'a' and 'z' inclusive using >= and <.