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JavaScript: Kth smallest number in a multiplication table

JavaScript Math: Exercise-111 with Solution

Write a JavaScript 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. Many educators believe it is necessary to memorize the table up to 9 x 9.
The illustration below shows a table up to 12 x 12, which is a size commonly used nowadays in English-world schools.

x 0 1 2 3 4 5 6 7 8 9 10 11 12
0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 0 1 2 3 4 5 6 7 8 9 10 11 12
2 0 2 4 6 8 10 12 14 16 18 20 22 24
3 0 3 6 9 12 15 18 21 24 27 30 33 36
4 0 4 8 12 16 20 24 28 32 36 40 44 48
5 0 5 10 15 20 25 30 35 40 45 50 55 60
6 0 6 12 18 24 30 36 42 48 54 60 66 72
7 0 7 14 21 28 35 42 49 56 63 70 77 84
8 0 8 16 24 32 40 48 56 64 72 80 88 96
9 0 9 18 27 36 45 54 63 72 81 90 99 108
10 0 10 20 30 40 50 60 70 80 90 100 110 120
11 0 11 22 33 44 55 66 77 88 99 110 121 132
12 0 12 24 36 48 60 72 84 96 108 120 132 144

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

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript program to Kth smallest number in a multiplication table</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function test(m, n, k) {
   if ((k<1)|| (k>m*n))
     return false;
    var s = 1, p = n*m
    while (s<= p) {
        var mid = s + Math.floor((p-s)/2)
        
      var t = 0
      for (i=1;i<=m;i++) {
        t += Math.min(Math.floor(mid/i),n)
      }
                
      if (t >= k) {
           p = mid - 1
        } else {
           s = mid + 1
        }
   }
    return s
}

m = 3
n = 3
k = 8
console.log("m = "+m+" : n = "+n+", k = "+k)
console.log("kth smallest element in m x n multiplication table: "+test(m,n,k));
m = 2
n = 3
k = 4
console.log("m = "+m+" : n = "+n+", k = "+k)
console.log("kth smallest element in m x n multiplication table: "+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:

JavaScript: Kth smallest number in a multiplication table.

Live Demo:

See the Pen javascript-math-exercise-111 by w3resource (@w3resource) on CodePen.


Improve this sample solution and post your code through Disqus

Previous: Sum of two square numbers equal to an integer.
Next: Maximum value swapping two digits in an integer.

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JavaScript: Tips of the Day

Shorten an array using its length property

A great way of shortening an array is by redefining its length property.

let array = [0, 1, 2, 3, 4, 5, 6, 6, 8, 9]
array.length = 4
// Result: [0, 1, 2, 3]

Important to know though is that this is a destructive way of changing the array. This means you lose all the other values that used to be in the array.

Ref: https://bit.ly/2LBj213