Problem

Nearly every one have used the Multiplication Table. But could you find out the k-th smallest number quickly from the multiplication table?

Given the height m and the length n of a m * n Multiplication Table, and a positive integer k, you need to return the k-th smallest number in this table.

Example 1:

Input: m = 3, n = 3, k = 5
Output:
Explanation:
The Multiplication Table:
1	2	3
2	4	6
3	6	9

The 5-th smallest number is 3 (1, 2, 2, 3, 3).


Example 2:

Input: m = 2, n = 3, k = 6
Output:
Explanation:
The Multiplication Table:
1	2	3
2	4	6

The 6-th smallest number is 6 (1, 2, 2, 3, 4, 6).


Note:

1. The m and n will be in the range [1, 30000].
2. The k will be in the range [1, m * n]

Solution 1: Nth element (MLE)

Time complexity: O(mn)

Space complexity: O(mn)

Solution2 : Binary Search

Find first x such that there are k elements less or equal to x in the table.

Time complexity: O(m*log(m*n))

Space complexity: O(1)

Related Problems

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