leetcode-169 多数元素 Python

方法一：

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        dic = {}
        for i in nums:
            dic[i] = dic.get(i, 0) + 1
            if dic[i] >= len(nums)/2:
                return i

方法二：

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        if not nums:
            return None
        dic = {}
        for i in nums:
            if i not in dic:
                dic[i] = 1
            else:
                dic[i] += 1 
        max = 0
        for key.val in dic.items():
            if val > max:
                max = val
                pos = key
        if max > int(len(nums)/2):
            return pos

方法三：

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        if not nums:
            return None
        dic = {}
        for i in nums:
            if i not in dic:
                dic[i] = 1
            else:
                dic[i] += 1 
        max = 0
        for key, val in dic.items():
            if val > max:
                max = val
                pos = key
        if max > int(len(nums)/2):
            return pos

方法四：投票算法

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

方法五：排序

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