find-majority-element.js

/*
Given an array of size n, find the majority element.
The majority element is the element that appears more than floor(n/2) times.
You may assume that the array is non-empty and the majority element always exist in the array.
*/

/*
This solution complexity is 
 worst case : o(n)
 best case: o(n/2) => though it is said as o(n), there is nothing wrong to mention as n/2 in best case
*/
function solution(A) {
    let length = A.length;
    switch (true) {
        case (length <= 1):
            return 0;
        case (length > 1):
            return getMajority(A);
        default:
            throw "I am weird case";
            break;
    }
}

function getMajority(A) {
    const obj = {};
    const highest = Math.floor(A.length / 2);
    let firstHighest = 0;
    let result = 0;
    for (let i = 0; i < A.length; i++) {
        let e = A[i];
        if (!obj[e])
            obj[e] = 1;
        else {
            obj[e] += 1;
            obj[e] > firstHighest ? (result = e, firstHighest = obj[e]) : firstHighest;
            if (firstHighest > Math.floor(A.length / 2)) {
                // console.log("I will break here beacuse, no need to procees");
                return result;
            }
        }
    }
    return result;
}
//solution([2,2,2,2,3,2,2,4,30,30,30,30,30,40]) => 2