1157. Online Majority Element In Subarray

Description

Design a data structure that efficiently finds the majority element of a given subarray.

The majority element of a subarray is an element that occurs threshold times or more in the subarray.

Implementing the MajorityChecker class:

• MajorityChecker(int[] arr) Initializes the instance of the class with the given array arr.
• int query(int left, int right, int threshold) returns the element in the subarray arr[left...right] that occurs at least threshold times, or -1 if no such element exists.

 

Example 1:

Input
["MajorityChecker", "query", "query", "query"]
[[[1, 1, 2, 2, 1, 1]], [0, 5, 4], [0, 3, 3], [2, 3, 2]]
Output
[null, 1, -1, 2]

Explanation
MajorityChecker majorityChecker = new MajorityChecker([1, 1, 2, 2, 1, 1]);
majorityChecker.query(0, 5, 4); // return 1
majorityChecker.query(0, 3, 3); // return -1
majorityChecker.query(2, 3, 2); // return 2

 

Constraints:

• 1 <= arr.length <= 2 * 104
• 1 <= arr[i] <= 2 * 104
• 0 <= left <= right < arr.length
• threshold <= right - left + 1
• 2 * threshold > right - left + 1
• At most 104 calls will be made to query.

Solution