K-th smallest prime fraction

May 20, 2023


Problem URL: K-th smallest prime fraction

We can use a heap to store the fractions. We can start with the fraction 1/n and add the next smallest fraction to the heap. We can repeat this process until we have added k fractions to the heap. The last fraction in the heap will be the k-th smallest fraction.

class Solution:
    def kthSmallestPrimeFraction(self, arr: List[int], k: int) -> List[int]:
        heap = []
        for i in range(len(arr)):
            heapq.heappush(heap, (arr[i]/arr[-1], i, len(arr)-1))

        while k > 1:
            _, i, j = heapq.heappop(heap)
            j -= 1
            if j > i:
                heapq.heappush(heap, (arr[i]/arr[j], i, j))
            k -= 1

        return arr[heap[0][1]], arr[heap[0][2]]

Time complexity: O(klog(n)) where n is the length of the array.
Space complexity: O(n) where n is the length of the array.