Trie Search Operation in DSA C++ - Execution Trace

Concept Flow - Trie Search Operation

Start at root node

↓

For each character in word

↓

Check if child node exists for char?

No→Word NOT found

Yes↓

Move to child node

↓

All chars processed?

No→Repeat for next char

Yes↓

Check if current node marks end of word?

↓

Yes

→Word FOUND

↓

No

→Word NOT found

The search starts at the root and checks each character's child node. If any character is missing, search fails. If all characters are found, it checks if the last node marks the end of a word.

Execution Sample

DSA C++

bool search(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 searches for a word in the trie by traversing nodes for each character and returns true if the word exists.

Execution Table

Step	Operation	Current Character	Child Exists?	Pointer Movement	Trie State Visual
1	Start search at root	-	N/A	current = root	root └─ c └─ a └─ t
2	Check first char 'c'	c	Yes	current = current->children['c' - 'a']	root └─ c └─ a └─ t
3	Check second char 'a'	a	Yes	current = current->children['a' - 'a']	root └─ c └─ a └─ t
4	Check third char 't'	t	Yes	current = current->children['t' - 'a']	root └─ c └─ a └─ t (endOfWord)
5	All chars processed, check endOfWord	-	N/A	N/A	Node 't' marks end of word: TRUE
6	Return result	-	N/A	N/A	Word FOUND

💡 Search ends after all characters are found and endOfWord is true, confirming the word exists.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
current	root	node for 'c'	node for 'a'	node for 't'	node for 't'
current->children[c - 'a']	N/A	exists	exists	exists	N/A
current->isEndOfWord	false	false	false	true	true

Key Moments - 3 Insights

Why do we check if the child node exists before moving the pointer?

Because if the child node for the current character does not exist, it means the word is not in the trie, so we must stop searching immediately.

Why do we check if the current node marks end of word after processing all characters?

Because a path may exist for all characters, but only nodes marked as endOfWord represent complete words. Step 5 shows this check to confirm the word exists.

What happens if the word is a prefix but not a complete word in the trie?

The search will find all characters but current->isEndOfWord will be false (Step 5), so the word is considered not found.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'current' after Step 3?

A Node for character 'c'

B Root node

C Node for character 'a'

D Node for character 't'

💡 Hint

Check the 'Pointer Movement' and 'Current Character' columns at Step 3 in execution_table.

At which step does the search confirm the word exists in the trie?

A Step 5

B Step 4

C Step 2

D Step 6

💡 Hint

Look at the 'Operation' and 'Trie State Visual' columns in execution_table for the endOfWord check.

If the child node for a character does not exist, what happens according to the execution flow?

A Search continues to next character

B Search returns false immediately

C Search marks endOfWord true

D Search restarts from root

💡 Hint

Refer to the concept_flow where the 'Child Exists?' check leads to 'Word NOT found' if No.

Concept Snapshot

Trie Search Operation:
- Start at root node
- For each character, move to child node if exists
- If any child missing, word not found
- After all chars, check if node marks end of word
- Return true if endOfWord is true, else false

Full Transcript

The trie search operation begins at the root node. For each character in the word, it checks if a child node exists. If a child node is missing, the search stops and returns false, meaning the word is not found. If all characters are found, it checks if the last node marks the end of a word. If yes, the search returns true, confirming the word exists in the trie. This process ensures only complete words are recognized, not just prefixes.