786 - K-th Smallest Prime Fraction\.

Medium

You are given a sorted integer array arr containing 1 and prime numbers, where all the integers of arr are unique. You are also given an integer k.

For every i and j where 0 <= i < j < arr.length, we consider the fraction arr[i] / arr[j].

Return the <code>k^th</code> smallest fraction considered. Return your answer as an array of integers of size 2, where answer[0] == arr[i] and answer[1] == arr[j].

Example 1:

Input: arr = 1,2,3,5, k = 3

Output: 2,5

Explanation: The fractions to be considered in sorted order are: 1/5, 1/3, 2/5, 1/2, 3/5, and 2/3. The third fraction is 2/5.

Example 2:

Input: arr = 1,7, k = 1

Output: 1,7

Constraints:

• 2 <= arr.length <= 1000

• <code>1 <= arri<= 3 * 10⁴</code>

• arr[0] == 1

• arr[i] is a prime number for i > 0.

• All the numbers of arr are unique and sorted in strictly increasing order.

• 1 <= k <= arr.length * (arr.length - 1) / 2

Follow up: Can you solve the problem with better than <code>O(n²)</code> complexity?