LeetCode 169 - Majority Element

• Difficulty: Easy.
• Related Topics: Array, Divide and Conquer, Bit Manipulation.
• Link: leetcode

Problem

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 1

/**
 * @param {number[]} nums
 * @return {number}
 */
var majorityElement = function (nums) {
  let map = {};
  let max = nums[0];
  for (let i = 0; i < nums.length; i++) {
    if (map[nums[i]]) {
      map[nums[i]] = map[nums[i]] + 1;
      if (map[max] < map[nums[i]]) {
        max = nums[i];
      }
    } else {
      map[nums[i]] = 1;
    }
  }
  return max;
};

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).