Leetcode - Kth Smallest Number in Multiplication Table

https://leetcode.com/problems/kth-smallest-number-in-multiplication-table/

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).

func findKthNumber(m int, n int, k int) int {
    low := 1
    high := m * n + 1
    var mid int
    for low < high {
        mid = low + (high - low)/2
        c := count(mid, m, n)
        if c >= k {
            high = mid
        } else {
            low = mid + 1
        }
    }
    
    return high
}

func count(mid, m, n int) int {
    c := 0
    for i := 1; i <= m; i++ {
        tmp := min(mid/i, n)
        c += tmp
    }
    return c
}

func min(a, b int) int {
    if a < b {
        return a
    }
    return b
}

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