# Kth Smallest Number in Multiplication Table in C++

Suppose we know about one Multiplication Table. But could we find out the k-th smallest number quickly from the multiplication table? So if we have to height m and the length n of a m * n Multiplication Table, and one positive integer k, we have need to find the k-th smallest number in this table.

So if m = 3 and n = 3 and k is 6, then the output will be 4., this is because the multiplication table is like −

 1 2 3 1 1 2 3 2 2 4 6 3 3 6 9

6th smallest element is 4 as [1,2,2,3,3,4,6,6,9]

To solve this, we will follow these steps −

• Define a function ok(), this will take m, n, x,
• ret := 0
• for initialize i := 1, when i <= n, update (increase i by 1), do −
• temp := minimum of x / i and m
• ret := ret + temp
• return ret
• From the main method, do the following −
• ret := -1, low := 1, high := m * n
• while low <= high, do −
• mid := low + (high - low) / 2
• cnt := ok(m, n, mid)
• if cnt >= k, then −
• high := mid - 1
• ret := mid
• Otherwise
• low := mid + 1
• return ret

Let us see the following implementation to get better understanding −

## Example

Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
int ok(int m, int n, int x){
int ret = 0;
for(int i = 1; i <= n; i++){
int temp = min(x / i, m);
ret += temp;
}
return ret;
}
int findKthNumber(int m, int n, int k) {
int ret = -1;
int low = 1;
int high = m * n ;
while(low <= high){
int mid = low + (high - low)/ 2;
int cnt = ok(m, n, mid);
if(cnt >= k){
high = mid - 1;
ret = mid;
}else low = mid + 1;
}
return ret;
}
};
main(){
Solution ob;
cout << (ob.findKthNumber(3,3,6));
}

## Input

“2*”

## Output

4