0169-majority-element

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Description

Given an array nums of size n, return the majority element.

The majority element is the element that appears more than ⌊n / 2⌋ times. You may assume that the majority element always exists in the array.

 

Example 1:

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

Example 2:

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

 

Constraints:

• n == nums.length
• 1 <= n <= 5 * 104
• -109 <= nums[i] <= 109
• The input is generated such that a majority element will exist in the array.

 

Follow-up: Could you solve the problem in linear time and in O(1) space?

Solution(Python)

class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        res = None
        cnt = 0
        for num in nums:
            if res is None or cnt == 0:
                res = num
                cnt = 1
            elif res == num:
                cnt += 1
            else:
                cnt -= 1
        return res