Is Majority Element II easy or hard?

Majority Element II is considered a Medium difficulty problem. The counting approach with a hash map is straightforward, but deriving the Boyer-Moore extension that tracks two candidates requires deeper understanding of voting and element cancellation techniques.

How to solve Majority Element II in O(n)?

Use the Boyer-Moore Voting Algorithm extension. Maintain two candidate values and their counters while iterating through the array. Elements cancel each other out when they differ from the current candidates. After the first pass, verify the remaining candidates with a second pass to ensure their counts exceed ⌊n/3⌋.

Majority Element II Python or Java solution?

Python and Java implementations typically use either a HashMap for counting frequencies or the Boyer-Moore voting extension for constant-space optimization. The hash map solution is simpler to implement, while the Boyer-Moore approach achieves O(n) time and O(1) space, which is preferred for interviews.

What is the best approach for Majority Element II?

The Boyer-Moore Voting Algorithm extension is the most efficient approach. It finds up to two candidates that may appear more than n/3 times by using a cancellation technique while iterating through the array. After identifying candidates, a second pass verifies their counts. This solution runs in O(n) time with O(1) extra space.

What data structure is used in Majority Element II?

Common solutions use either a hash table or constant-space counters. The hash map approach stores element frequencies for quick lookup, while the Boyer-Moore algorithm tracks two candidate elements and their counts without extra storage. Both operate on a simple array traversal.

What is the time complexity of Majority Element II?

The optimal solution runs in O(n) time because the array is scanned at most twice—once to determine potential candidates and once to verify their frequencies. The space complexity is O(1) when using the Boyer-Moore voting approach. A hash map counting method also runs in O(n) time but requires O(n) space.

Is Majority Element II asked at Google, Amazon, or Meta?

Majority Element II appears in coding interview practice sets and has been reported in interview preparation resources for companies like Amazon and Meta. The problem tests understanding of array traversal, frequency counting, and the Boyer-Moore voting algorithm—concepts commonly evaluated in technical interviews.