169. Majority Element

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

Solution

    public int majorityElement(int[] nums) {
        HashMap<Integer, Integer> m = new HashMap<>();
        for (int n : nums) {
            m.put(n, m.getOrDefault(n, 0) + 1);
        }
        Optional<Map.Entry<Integer, Integer>> maxEntry = m.entrySet()
                .stream()
                .max(Comparator.comparing(Map.Entry::getValue));
        return maxEntry.get()
                .getKey();
    }

better solution

public int majorityElement(int[] nums) {
    int major = 0, count = 0;
    for (int i = 0; i < nums.length; i++) {
        if (count == 0) major = nums[i];
        if (major == nums[i]) count++;
        else count--;
    }
    return major;
}

reference: https://leetcode.com/problems/majority-element/description/?source=submission-ac