PermMissingElem.py #Codility Solutions

PermMissingElem.py

# you can write to stdout for debugging purposes, e.g.
# print "this is a debug message"

def solution(A):
    # write your code in Python 2.7
    # input validation

    # empty input
    if not len(A):
        return 1

    # single input
    if len(A) == 1:
        if 1 in A:
            return A[0]+1
        else:
            return 1

    # solution
    minimum = min(A)
    maximum = max(A)

    if minimum <= 0:
        return 1
    
    if minimum > 1:
        return minimum - 1
    
    B = [_ for _ in range(minimum, maximum + 1)]
    C = set(B) - set(A)
    C = list(C)

    # output validation
    if not len(C):
        return maximum + 1

    if len(C) == 1:
        return C[0]
    else:
        mi = min(C) - 1
        ma = max(C) + 1
        return mi if mi >= 0 else ma