719 - heap

class Solution:
    def smallestDistancePair(self, nums: List[int], k: int) -> int:
        nums.sort()

        h = [(abs(nums[i] - nums[i+1]), i, i + 1) for i in range(len(nums) - 1)]
        heapq.heapify(h)

        while k:
            cur, i, j = heapq.heappop(h)
            if j + 1 < len(nums):
                heapq.heappush(h, (abs(nums[i]-nums[j+1]), i, j+1))
            k -= 1
        return cur