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C Programming: Kth smallest number in a multiplication table

C Programming Mathematics: Exercise-34 with Solution

Write a C program that creates a multiplication table of size m x n using integers where 1 <= k <= m * n. Return the kth smallest element in the said multiplication table.

In mathematics, a multiplication table is a mathematical table used to define a multiplication operation for an algebraic system. The decimal multiplication table was traditionally taught as an essential part of elementary arithmetic around the world, as it lays the foundation for arithmetic operations with base-ten numbers.

Test Data:
(3,3,8) -> 6
(2,3,4) -> 3

Sample Solution:

C Code:

#include <stdio.h>
#include <math.h>

int min(int a, int b)
 {
 	return (a > b) ? b : a;
 }
int test(int m, int n, int k) {
   if ((k<1)|| (k>m*n))
     return false;
    int s, p, mid, t;
	s = 1, p = n*m;
    while (s<= p) {
      mid = s + floor((p-s)/2);
      t = 0;
      for (int i=1;i<=m;i++) {
        t += min(floor(mid/i),n);
      }
                
      if (t >= k) {
           p = mid - 1;
        } 
	  else {
           s = mid + 1;
        }
   }
    return s;
}
int main(void) {
  int m = 3;
  int n = 3;
  int k = 8;
  printf("m = %d, n = %d  k = %d",m,n,k);
  printf("\nkth smallest element in m x n multiplication table = %d", test(m,n,k));	
  m = 2;
  n = 3;
  k = 4;
  printf("\n\nm = %d, n = %d  k = %d",m,n,k);
  printf("\nkth smallest element in m x n multiplication table = %d", test(m,n,k));	
} 


Sample Output:

m = 3, n = 3  k = 8
kth smallest element in m x n multiplication table = 6
m = 2, n = 3  k = 4
kth smallest element in m x n multiplication table = 3

Flowchart:

Flowchart: Kth smallest number in a multiplication table

C Programming Code Editor:

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Next: Find all prime factors of a given integer.

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C Programming: Tips of the Day

What's the point of const pointers?

const is a tool which you should use in pursuit of a very important C++ concept:

Find bugs at compile-time, rather than run-time, by getting the compiler to enforce what you mean.

Even though it does not change the functionality, adding const generates a compiler error when you're doing things you didn't mean to do. Imagine the following typo:

void foo(int* ptr)
{
    ptr = 0;// oops, I meant *ptr = 0
}

If you use int* const, this would generate a compiler error because you're changing the value to ptr. Adding restrictions via syntax is a good thing in general. Just don't take it too far -- the example you gave is a case where most people don't bother using const.

Ref : https://bit.ly/33Cdn3Q