PYTHON

OddOccurrencesInArray

//correctness 100% perfomance 25%
def solution(A):
    for number in A:
        if number != '-':
            A[A.index(number)] = '-'
            if number in A:
                A[A.index(number)] = '-'
            else:
                return number

A= [9,3,9,3,9,7,9]
solution(A)