Smallest Positive Integer Coding Problem (Javascript)

September 3, 2020

Write a function:

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].

Solution:

function solution(A) {
  // write your code in JavaScript (Node.js 8.9.4)
  A.sort((a, b) => a - b);
  let min = 1;
  for (let i = 0; i < A.length; i++) {
    let newValue = A[i];
    if (newValue === min) {
      min += 1;
    } else if (newValue > min) {
      return min;
    }
  }

  return min;
}