Most Frequent String in an Array

Problem Given an array of strings, find the string that occurs most frequently.

Input / Output

• Input: array words of strings.
• Output: the most frequently occurring string. Clarify tie-breaking with the interviewer — first occurrence, lexicographically smallest, or any.

Constraints

• Up to ~10^5 strings, duplicates expected.
• Strings may be of arbitrary length k, which matters: hashing a string is O(k), not O(1).
• The array may be empty — decide the contract (null, exception, or sentinel).

Example

• Input: ["hello", "world", "world", "bar", "hello", "hello"] → Output: "hello" (frequency 3).
• Tricky case: ["a", "b"] — an all-distinct array where every count is 1, so the tie-break rule decides the answer. This is the clarifying question worth asking up front.