Write a function: class Solution { public int solution(int[] A); } that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.
For example:
- Given A = [1, 3, 6, 4, 1, 2], the function should return 5;
- Given A = [1, 2, 3], the function should return 4;
- Given A = [−1, −3], the function should return 1.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [1..100,000];
- Each element of array A is an integer within the range [−1,000,000..1,000,000].
private static int Solution(int[] A)
{
int num = 1;
if (A == null || A.Length == 0)
return num;
var set = new HashSet<int>(A);
while (set.Contains(num))
{
num++;
}
return num;
}