Trie Search Operation in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the current character exists in the children dictionary.

DSA C#

if (!node.children.ContainsKey([1]))
{
    return false;
}

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

Aword[i]

Bword

Ci

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole word instead of a single character.

Using the index i directly instead of word[i].

We check if the current character word[i] exists as a key in the children dictionary.

2fill in blank

medium

Complete the code to move to the next node in the Trie for the current character.

DSA C#

node = node.children[[1]];

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Ai

Bword

Cword[i]

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Using the index i instead of the character word[i].

Using the whole word as key.

We update node to the child node corresponding to the current character word[i].

3fill in blank

hard

Fix the error in the return statement to correctly check if the word ends here.

DSA C#

return node.[1];

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AwordEnd

BisEnd

CendOfWord

DisWord

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names like isEnd or endOfWord.

Returning the wrong property causing incorrect search results.

The boolean property isWord indicates if the current node marks the end of a valid word.

4fill in blank

hard

Fill both blanks to complete the for loop that iterates over each character in the word.

DSA C#

for (int [1] = 0; [2] < word.Length; [1]++)
{
    // loop body
}

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Ai

Bj

Ck

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in initialization and condition.

Using variable names not matching the loop body.

The loop variable i is used consistently for initialization and condition check.

5fill in blank

hard

Fill all three blanks to complete the search method for the Trie.

DSA C#

public bool Search(string word)
{
    TrieNode node = root;
    for (int [1] = 0; [2] < word.Length; [1]++)
    {
        if (!node.children.ContainsKey(word[[3]]))
            return false;
        node = node.children[word[[3]]];
    }
    return node.isWord;
}

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

Ai

Bj

Ck

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variables for loop and indexing causing errors.

Using variables not declared in the loop.

The loop variable i is used consistently for iteration and indexing characters in the word.

Practice

1. What does the Search operation in a Trie data structure do?

easy

A. Checks if a given word exists in the Trie

B. Inserts a new word into the Trie

C. Deletes a word from the Trie

D. Counts the total words stored in the Trie

Solution

1. Step 1: Understand the purpose of Search in Trie

   The Search operation is designed to check if a specific word is present in the Trie data structure.

2. Step 2: Differentiate from other operations

   Insertion adds words, deletion removes words, and counting totals words. Search only checks existence.

3. Final Answer:

   Checks if a given word exists in the Trie -> Option A

4. Quick Check:

   Search = Check word presence [OK]

Hint: Search checks presence, not insertion or deletion [OK]

Common Mistakes:

• Confusing search with insert operation
• Thinking search deletes words
• Assuming search counts words

2. Which of the following is the correct C# method signature for a Trie search operation that returns a boolean?

easy

A. public void Search(string word)

B. public bool Search(string word)

C. public int Search(string word)

D. public string Search(string word)

Solution

1. Step 1: Identify return type for search

   Search should return true or false indicating if the word exists, so return type must be bool.

2. Step 2: Check method signature correctness

   Method takes a string parameter for the word and returns bool, matching "public bool Search(string word)".

3. Final Answer:

   public bool Search(string word) -> Option B

4. Quick Check:

   Search returns bool for word presence [OK]

Hint: Search returns true/false, so return type is bool [OK]

Common Mistakes:

• Using void return type for search
• Returning int or string instead of bool
• Incorrect method parameter types

3. Given the following Trie search code snippet, what will be the output when searching for the word "cat" after inserting "car" and "cat"?

Trie trie = new Trie();
trie.Insert("car");
trie.Insert("cat");
Console.WriteLine(trie.Search("cat"));
Console.WriteLine(trie.Search("cap"));

medium

A. False
True

B. True
True

C. True
False

D. False
False

Solution

1. Step 1: Analyze inserted words

   Words "car" and "cat" are inserted, so both exist in the Trie.

2. Step 2: Check search results for "cat" and "cap"

   "cat" exists, so search returns true; "cap" was not inserted, so search returns false.

3. Final Answer:

   True False -> Option C

4. Quick Check:

   Search("cat")=True, Search("cap")=False [OK]

Hint: Inserted words return true; others return false [OK]

Common Mistakes:

• Assuming "cap" exists after inserting "car" and "cat"
• Mixing output order
• Confusing true/false outputs

4. Identify the bug in this Trie search method that causes it to always return false:

public bool Search(string word) {
    TrieNode node = root;
    foreach (char c in word) {
        if (!node.Children.ContainsKey(c))
            return false;
        node = node.Children[c];
    }
    return false;
}

medium

A. The method should return true immediately after first character check

B. It should return false if node.Children contains the character

C. The foreach loop should iterate over node.Children keys

D. It should return true after checking all characters if node marks end of word

Solution

1. Step 1: Understand the search logic

   The method checks each character in the word exists in the Trie nodes.

2. Step 2: Identify the missing return condition

   After the loop, it always returns false instead of checking if the current node marks the end of a valid word.

3. Final Answer:

   It should return true after checking all characters if node marks end of word -> Option D

4. Quick Check:

   Return true if end of word reached [OK]

Hint: Return true only if end of word node reached [OK]

Common Mistakes:

• Returning false unconditionally after loop
• Not checking end of word flag
• Returning true too early

5. You want to modify a Trie search operation to support prefix search (checking if any word starts with a given prefix). Which change is correct?

hard

A. Return true as soon as all prefix characters are found, without checking end of word

B. Return true only if the prefix is also a complete word in the Trie

C. Return false if any character in prefix is found

D. Return true only if prefix length equals word length

Solution

1. Step 1: Understand prefix search goal

   Prefix search should confirm if the Trie contains any word starting with the given prefix.

2. Step 2: Adjust search logic for prefix

   Return true immediately after all prefix characters are found, no need to check if prefix is a complete word.

3. Final Answer:

   Return true as soon as all prefix characters are found, without checking end of word -> Option A

4. Quick Check:

   Prefix found = true without full word check [OK]

Hint: Prefix search returns true once prefix path exists [OK]

Common Mistakes:

• Checking end of word for prefix search
• Returning false if prefix is not a full word
• Confusing prefix search with full word search