0378.Kth-smallest-element-in-a-sorted-matrix

0378. Kth Smallest Element in a Sorted Matrix

Given an n x n matrix where each of the rows and columns are sorted in ascending order, return *the kth smallest element in the matrix9.

Note that it is the kth smallest element in the sorted order, not the kth distinct element.

Example 1:

Input: matrix = [[1,5,9],[10,11,13],[12,13,15]], k = 8
Output: 13
Explanation: The elements in the matrix are [1,5,9,10,11,12,13,13,15], and the 8th smallest number is 13

Example 2:

Input: matrix = [[-5]], k = 1
Output: -5