def is_duplicate_v1(A):
    N = len(A)
    for i in range(N):
        for j in range(i + 1, N):
            if A[i] == A[j]:
                return True
    return False

def is_duplicate_v2(A):
    seen = []
    for item in A:
        if item in seen:
            return True
        seen.append(item)
    return False
