Leetcode 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.

 

Runtime: O(n) — Moore voting algorithm: We maintain a current candidate and a counter initialized to 0. As we iterate the array, we look at the current element x:

If the counter is 0, we set the current candidate to x and the counter to 1.

If the counter is not 0, we increment or decrement the counter based on whether x is the current candidate.

After one pass, the current candidate is the majority element. Runtime complexity = O(n).

var majorityElement = function(nums) {

    var candidate = 0

    var checker = 0

    for(var i=0;i<nums.length;i++){

        if(checker===0){

            candidate = nums[i]

            checker++

        }

        else{ 

            if(nums[i] === candidate)

                checker++

            else

                checker--

        }

    }

    return candidate

}