Demo Test

This is a demo task.

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].

public int solution(int[] A) {
        Set<Integer> nums = new HashSet<>();
        for(int a : A) {
            if (a > 0) {
                nums.add(a);
            }
        }
        for (int i = 1; i <= A.length + 1; i++) {
            if (!nums.contains(i)) {
                return i;
            }
        }
        return 1;
    }