LeetCode Notes: Majority Element

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Question

Given an array nums of size n, return the majority element.

The majority element is the element that appears more than ⌊n / 2βŒ‹ times. You may assume that the majority element always exists in the array.

Example 1:

Input: nums = [3,2,3]

Output: 3

Example 2:

Input: nums = [2,2,1,1,1,2,2]

Output: 2

Constraints:

  • n == nums.length
  • 1 <= n <= 5 * 104
  • -231 <= nums[i] <= 231 - 1

Follow-up: Could you solve the problem in linear time and in O(1) space?

Solution

Code:

/**
 * @param {number[]} nums
 * @return {number}
 */
var majorityElement = function(nums) {
    const result = [] //result array
    const obj = {} //count

    // Count the number of occurrences of each number
    nums.forEach((ele)=>{
        if(ele in obj){
            obj[ele] += 1
        }else{
            obj[ele] = 1
        }
    })

    // Determine whether the conditions are met
    for(let key in obj){
        if(obj[key] > nums.length / 2){
            result.push(key)
        }
    }

    return result
};

Reference

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