Smallest-positive-integer

Given an array A of N integers
For Example:
Input: {2, 3, 7, 6, 8, -1, -10, 15}
Output: 1
Input: { 2, 3, -7, 6, 8, 1, -10, 15 }
Output: 4
Input: {1, 1, 0, -1, -2}
Output: 2

It will return the smallest positive integer (greater than 0) that does not occur in A.

Complexity of written code is O(nlogn)