Word Search in Trie in DSA C++ - Execution Trace

Concept Flow - Word Search in Trie

Start at root node

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For each character in word

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Check if character exists in current node's children

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Move to child node

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Repeat for next character

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After last character

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Check if current node marks end of word

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Word FOUND

Start from root, check each character in the word by moving through child nodes. If all characters match and last node marks word end, word is found.

Execution Sample

DSA C++

bool searchWord(TrieNode* root, string word) {
  TrieNode* current = root;
  for (char c : word) {
    if (!current->children[c - 'a']) return false;
    current = current->children[c - 'a'];
  }
  return current->isEndOfWord;
}

This code checks if a word exists in the trie by traversing nodes for each character.

Execution Table

Step	Operation	Current Character	Node Exists?	Move Pointer	Visual State
1	Start at root	-	N/A	current = root	root
2	Check 'c'	'c'	Yes	current = node for 'c'	root -> c
3	Check 'a'	'a'	Yes	current = node for 'a'	root -> c -> a
4	Check 't'	't'	Yes	current = node for 't'	root -> c -> a -> t
5	End of word check	-	N/A	Check isEndOfWord at 't'	root -> c -> a -> t (isEndOfWord = true)
6	Result	-	N/A	Return true	Word found
7	Start at root	-	N/A	current = root	root
8	Check 'd'	'd'	Yes	current = node for 'd'	root -> d
9	Check 'o'	'o'	No	Return false	root -> d (no 'o' child)
10	Result	-	N/A	Return false	Word not found

💡 Traversal stops when a character node is missing or after checking last character's end marker.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	After Step 8	After Step 9
current	root	node 'c'	node 'a'	node 't'	node 't'	node 'd'	node 'd'
current->isEndOfWord	false	false	false	true	true	false	false

Key Moments - 3 Insights

Why do we return false immediately when a character node does not exist?

Because if the trie does not have a child node for the current character (see Step 9 in execution_table), the word cannot be formed, so we stop searching.

Why do we check isEndOfWord after the last character?

Because the path may exist but might not represent a complete word. Only if isEndOfWord is true (Step 5) do we confirm the word exists.

What happens if the word is empty?

The search starts and ends at root. Since no characters are checked, the result depends on whether root marks end of a word, usually false.

Visual Quiz - 3 Questions

Look at the execution_table, what is the current node after Step 3 when searching 'cat'?

A Node for 'c'

B Node for 'a'

C Node for 't'

D Root node

💡 Hint

Check the 'Move Pointer' and 'Visual State' columns at Step 3 in execution_table.

At which step does the search for 'dog' fail due to missing node?

A Step 9

B Step 8

C Step 7

D Step 10

💡 Hint

Look for 'Node Exists?' column showing 'No' in execution_table.

If the last node's isEndOfWord was false for 'cat', what would be the search result?

A Word found

B Partial match found

C Word not found

D Error in trie

💡 Hint

Refer to Step 5 and Step 6 in execution_table about isEndOfWord check.

Concept Snapshot

Word Search in Trie:
- Start at root node
- For each character, move to child node if exists
- If any character missing, word not found
- After last char, check isEndOfWord flag
- Return true if flag set, else false

Full Transcript

This visual execution shows how to search a word in a trie. We start at the root node and check each character of the word one by one. If the current character exists as a child node, we move the pointer to that node. If not, we stop and return false because the word cannot be formed. After checking all characters, we verify if the last node marks the end of a word. If yes, the word is found; otherwise, it is not. The execution table traces searching 'cat' successfully and 'dog' failing at the second character. Variable tracker shows how the current pointer moves through nodes. Key moments clarify why missing nodes cause immediate failure and why the end-of-word flag matters. The quiz tests understanding of pointer movement, failure step, and end-of-word significance.