LeetCode-in-All

169. Majority Element

Easy

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

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

Solution

-spec majority_element(Nums :: [integer()]) -> integer().
majority_element(Nums) ->
    element(1, lists:foldl(
        fun(Num, {Candi, Cnt}) -> 
            NewCandi = if Cnt == 0 -> Num; true -> Candi end,
            NewCnt = if NewCandi == Num -> Cnt + 1; true -> Cnt - 1 end,
            {NewCandi, NewCnt}
        end,
        {0, 0},
        Nums
    )).

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