Smallest Common Multiple - Can someone explain this solution?

JavaScript
1

Can anyone help me explain how this solution works? This is one of the solutions of the problem from :
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/smallest-common-multiple

Here is the solution :

function smallestCommons(arr) {

  var max = Math.max(arr[0], arr[1]);
  var min = Math.min(arr[0], arr[1]);
  var mltple = max;

  for(var i = max; i >= min; i--){
    if(mltple % i !== 0){
      mltple += max; 
      i = max;
    } 
  }

  return mltple;  
}


console.log(smallestCommons([1,5]));

Here is the explanation I can come up with.

// max = 5
//min = 1

//mltiple = 5;

/* for (i = 5 ; 5 >= 1 ; i-- )  {
   if (5 % 5 !==0 ) = answer is 0, false  
   if (5 % 4 !==0 ) answer is 1, 1st true
   if (5 % 3 !==0 ) answer is 2, 2nd true
   if (5 % 2 !==0 ) answer is 1, 3rd true
   if (5 % 1 !==0 ) answer is 0 , false
    5 = 5(This is the original Multiple) + 5(1st true) + 5(2nd true) + 5(3rd true)   = This should be 20
            5 = 5 --> What does this do?
            4 = 5 --> What does this do?
            3 = 5 --> What does this do?
            2 = 5 --> What does this do?
            1 = 5 --> What does this do?
}

return mltple should be equal to 20?

*/

This will be a big help if someone can explain it.

Thanks.

2

It works. You can throw in some console log statements to see what’s happening to i and mltple as the for loop executes.

The basic idea is that whatever the smallest common multiple is, it will be a multiple of max. So the code just checks every single multiple of max starting from the lowest until it reaches one that can be evenly divided by all the integers between max and min.

For the case where max = 5 and min = 1, it would go like this (in plain English):

mltple == 5

  • Is 5 divisible by 5? Yep. Go on!.
  • Is 5 divisible by 4? Nope. Add 5 to mltple and reset the for loop

mltple == 10

  • Is 10 divisible by 4? Nope. Add 5 to mltple and reset the for loop

mltple == 15

  • Is 15 divisible by 4? Nope. Add 5 to mltple and reset the for loop

mltple == 20

  • Is 20 divisible by 4? YES, finally. Go on!
  • Is 20 divisible by 3? Nope. Add 5 to mltple and reset the for loop.

mltple == 25

  • Is 25 divisible by 4? Nope. Add 5 to mltple and reset the for loop.

…and so on through 30, 35, 40, 45, 50, and 55 until we reach 60, where it will go like this:

mltple == 60

  • Is 60 divisible by 4? Yes. Go on!
  • Is 60 divisible by 3? Yes. Go on!
  • Is 60 divisible by 2? Yes. Go on!
  • Is 60 divisible by 1? Yes. Go on!

ALL DONE! LET’S GO GET A BEER OR SOME GUMMY BEARS!

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