Demo Test

Problem

function solution(A);

function solution(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].

My Solution

function solution(A) {
	let isPositive = A.some((item) => item > 0);

	if (!isPositive) {
		return 1;
	} else {
		let optimizedArr = new Set(A);
		let max = Math.max(...A);
		let min = Math.min(...A);

		for (let i = min; i < max + 1; i++) {
			if (!optimizedArr.has(i)) return i;
		}

		return max + 1;
	}
}