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.

Example 1:

Input: [3,2,3]
Output: 3

Example 2:

Input: [2,2,1,1,1,2,2]
Output: 2

来自 <https://leetcode.com/problems/majority-element/description/>

 

思路1：记录下每个元素出现的次数，并以键值对的形式存放在字典中，找出次数最高的那个元素 

class Solution(object):
    def majorityElement(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        m_dict = {}
        for i in nums:
            if i in m_dict.keys():
                m_dict[i] += 1
            else:
                m_dict[i] = 1
        values = list(m_dict.values())
        id=values.index(max(values))
        return list(m_dict.keys())[id]

 

思路2：对所有元素进行排序，在排序中位于length/2位置上的一定是出现次数超过一半的那个 

class Solution(object):
    def majorityElement(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        return sorted(nums)[len(nums)//2]