LeetCode-in-All

169. Majority Element

Easy

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

The majority element is the element that appears more than ⌊n / 2⌋ 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
• -109 <= nums[i] <= 109

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

Solution

/**
 * @param {number[]} nums
 * @return {number}
 */
var majorityElement = function(arr) {
    let count = 1
    let majority = arr[0]

    for (let i = 1; i < arr.length; i++) {
        if (arr[i] === majority) {
            count++;
        } else if (count > 1) {
            count--;
        } else {
            majority = arr[i];
        }
    }

    count = 0
    for (const num of arr) {
        if (num === majority) {
            count++
        }
    }

    if (count >= Math.floor(arr.length / 2) + 1) {
        return majority
    } else {
        return -1
    }
};

export { majorityElement }

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