g0301_0400.s0378_kth_smallest_element_in_a_sorted_matrix

Class Solution

java.lang.Object

g0301_0400.s0378_kth_smallest_element_in_a_sorted_matrix.Solution

public class Solution
extends Object

378 - Kth Smallest Element in a Sorted Matrix.

Medium

Given an n x n matrix where each of the rows and columns is 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.

You must find a solution with a memory complexity better than O(n2).

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 8^th smallest number is 13

Example 2:

Input: matrix = -5, k = 1

Output: -5

Constraints:

• n == matrix.length == matrix[i].length
• 1 <= n <= 300
• -109 <= matrix[i][j] <= 109
• All the rows and columns of matrix are guaranteed to be sorted in non-decreasing order.
• 1 <= k <= n2

Follow up:

• Could you solve the problem with a constant memory (i.e., O(1) memory complexity)?
• Could you solve the problem in O(n) time complexity? The solution may be too advanced for an interview but you may find reading this paper fun.

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	kthSmallest(int[][] matrix, int k)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

kthSmallest

public int kthSmallest(int[][] matrix,
                       int k)