Majority Element

Description

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

Example 1:

Input: [3,2,3]
Output: 3

Example 2:

Input: [2,2,1,1,1,2,2]
Output: 2

Solution(javascript)

// Boyer-Moore Voting Algorithm O(n) time O(1) Space
const majorityElement = function (nums = []) {
  return nums.reduce(([candidate, count], num) => {
    if (candidate === num) {
      return [candidate, count + 1]
    }
    if (count - 1 < 0) {
      return [num, 1]
    }
    return [candidate, count - 1]
  }, [nums[0], 0])[0]
}