https://leetcode-cn.com/problems/majority-element/
    很简单
    1.可以先排序，返回中间的元素
    2.利用map

    1. class Solution {
    2.     public int majorityElement(int[] nums) {
    3.         int res = nums[0];
    4.         Map<Integer,Integer> map = new HashMap<>();
    5.         for(int i=0; i<nums.length; i++){
    6.             if(map.containsKey(nums[i])){
    7.                 map.put(nums[i], map.get(nums[i])+1);
    8.             }else{
    9.                 map.put(nums[i], 1);
    10.             }
    11.         }
    12.         for(Integer key: map.keySet()){
    13.             if((map.get(key))>(nums.length/2)){
    14.                 res = key;
    15.             }
    16.         }
    17.         return res;
    18.     }
    19. }