Sender With Largest Word Count

Sender With Largest Word Count

What is this problem about?

The Sender With Largest Word Count interview question gives you two arrays of equal length: messages and senders. Each message is a string of words sent by the corresponding sender. Your task is to find the sender who sent the most words in total. If there is a tie, return the sender who is lexicographically largest. This is a hash table counting problem with a tiebreak.

Why is this asked in interviews?

Google asks this problem because it combines hash map aggregation with string processing and comparison logic. It tests whether candidates can cleanly build a frequency map (word count per sender), handle the tiebreak condition (lexicographic maximum), and avoid off-by-one errors when counting words. The problem models real-world analytics tasks like finding the most active user in a messaging system.

Algorithmic pattern used

The pattern is hash table counting with argmax. For each message messages[i] sent by senders[i], compute the word count: len(messages[i].split()). Add it to a running total in a dictionary word_count[sender]. After processing all messages, find the sender with the maximum total word count. On ties, keep the lexicographically larger sender name. This is O(total words) time and O(unique senders) space.

Example explanation

Messages: ["Hello World", "Hi", "Go go go"], senders: ["Alice", "Bob", "Alice"].

Word counts:

• Alice: 2 (Hello World) + 3 (Go go go) = 5.
• Bob: 1 (Hi).

Maximum word count: Alice with 5 words. Return "Alice".

Tiebreak example: Alice=5, Charlie=5.

• Lexicographically larger: "Charlie" > "Alice" → return "Charlie".

Common mistakes candidates make

• Counting characters instead of words — use .split() not len(message).
• Handling the tiebreak with >= instead of > when updating the best sender — >= would incorrectly prefer the last seen sender alphabetically instead of the lexicographically largest.
• Not initializing the dictionary with defaultdict(int) or get(key, 0), causing KeyError.
• Not comparing sender names as strings for the lexicographic tiebreak — remember Python string comparison is lexicographic by default.

Interview preparation tip

For the Sender With Largest Word Count coding problem, the hash table counting string interview pattern is the core skill. Python's collections.Counter and defaultdict both work cleanly for this problem. Google interviewers appreciate concise solutions — a single pass with a running maximum and tiebreak check avoids a separate argmax step. Practice this "find key with maximum value, tiebreak by key order" pattern — it appears in "top contributor" and "most active user" analytics queries across many interviews.