Codility : PermMissingElem Python Exercise


A zero-indexed array A consisting of N different integers is given. The array contains integers in the range [1..(N + 1)], which means that exactly one element is missing.

Your goal is to find that missing element.

Write a function:

    def solution(A)

that, given a zero-indexed array A, returns the value of the missing element.

For example, given array A such that:
A[0] = 2 A[1] = 3 A[2] = 1 A[3] = 5

the function should return 4, as it is the missing element.

Assume that:

        N is an integer within the range [0..100,000];
        the elements of A are all distinct;
        each element of array A is an integer within the range [1..(N + 1)].


        expected worst-case time complexity is O(N);
        expected worst-case space complexity is O(1), beyond input storage (not counting the storage required for input arguments).

Python solution:

def solution(A):
    # write your code in Python 2.7
    if not A:
        return 1
    if 1 not in A:
        return 1
    if len(A)==1:
        return A[0]+1
    for i in range(0,len(A)-1):
        if (A[i+1]-A[i]) !=1:
            return A[i]+1
    return A[i+1]+1


You can find python solution on my github account March 23, 2016, 4:10 p.m.