0786. K-th Smallest Prime Fraction

https://leetcode.com/problems/k-th-smallest-prime-fraction

Description

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 kth 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

• 1 <= arr[i] <= 3 * 104

• 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

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