n x n
matrix where each of the rows and columns are sorted in ascending order, return the
kth smallest element in the matrix.
Note that it is the
kth smallest element in the sorted order, not the
kth distinct element.
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
Input: matrix = [[-5]], k = 1 Output: -5
n == matrix.length
n == matrix[i].length
1 <= n <= 300
-109 <= matrix[i][j] <= 109
matrixare guaranteed to be sorted in non-decreasing order.
1 <= k <= n2