[Codility] Lesson 4 - Counting Elements : MissingInteger

Lesson 4 - Counting Elements : MissingInteger

📌 문제

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].

📝 풀이

• 주어진 A 를 오름차순으로 정렬한다.
• 기본값은 1 에서 A 에서 같은 값이 있을 때마다 1을 더해준다.

💻 구현

static class Solution{
    public int solution(int[] A){
        int answer = 1;
        Arrays.sort(A);

        for(int i = 0; i < A.length; i++){
            if(answer == A[i]) answer++;
        }

        return answer;
    }
}