Perm-Missing-Element with python

Question

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)].

Complexity:

• 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).

Elements of input arrays can be modified.

Solution

#given array a={2,3,1,5}
#so the function name is solution with A as argument...

def solution(A):

#length and xor sum value we are initailsing.....

    length = len(A)

#length is length of A

    xor_sum = 0

    for index in range(0, length):

#^ is the operator of XOR in python

#so in the xor_sum statement it may be be xor_sum or A[index] or index+1

        xor_sum = xor_sum ^ A[index] ^ (index + 1)

    return xor_sum^(length + 1)