169. Majority Element

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.

给定一个数组，找这个数组中的主元素，主元素是元素出现次数大于⌊ n/2 ⌋的元素。 假设给定的数组非空，主元素都存在。 

    public int majorityElement(int[] nums) {
        Map<Integer, Integer> numberMap = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            numberMap.put(nums[i], numberMap.getOrDefault(nums[i], 0)+1);
        }
        int level = (nums.length+1)/2;
        for (Map.Entry<Integer, Integer> e : numberMap.entrySet()) {
            if (e.getValue() >= level) {
               return e.getKey();
            }
        }
        return Integer.MIN_VALUE;        
    }