leetcode：多数元素

方法一：哈希表

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        counts = collections.Counter(nums)  #计数函数 {元素：次数}
        return max(counts.keys(), key = counts.get) #比较所有的值  返回键

方法二：排序

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        nums = sorted(nums)
        return nums[len(nums)//2]
        

方法三：摩尔投票法

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        res = 0
        count = 0 
        for num in nums :
            if count == 0 :
                res = num
            if res == num :
                count += 1
            else :
                count -= 1
        return res