251. OddOccurrencesInArray

1. JavaScript

function solution(A) {
    // write your code in JavaScript (Node.js 8.9.4)
    let element = new Set();
    
    for(let i in A){
        if(!element.has(A[i])){
            element.add(A[i]);
        }
        else{
            element.delete(A[i]);
        }
    }
    
    const result = [...element];
    return result[0];
}

2. Python

def test3(A):
    if len(A) == 1:
        return A[0]

    A = sorted(A)
    print(A)
    for i in range(0, len(A), 2):
        if i+1 == len(A):
            return A[i]
        if A[i] != A[i+1]:
            return A[i]

test3([1,2,1,2,3])