Search dublicate

example.py

arr = [1,2,1,5,2,1,3,2,4]
# arr = [1,2,3,4]

class MyException(ValueError): 
    pass

def dublicate(arr, repeat = []):
    if not arr:
        raise MyException("Exception None dublicate")
    elif arr[0] in repeat:
        return arr[0]
    else:
        if arr.count(arr[0]) >= 2:
            repeat.append(arr[0])
        return dublicate(arr[1:])


res = dublicate(arr)

print(res)