2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. Write a function called smallest_multiple that returns a uint64, the smallest positive number that is evenly divisible by all of the numbers fr

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Emma Sellers 2019-1-8

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https://ww2.mathworks.cn/matlabcentral/answers/438796-2520-is-the-smallest-number-that-can-be-divided-by-each-of-the-numbers-from-1-to-10-without-any-rema

评论： Steven Lord 2019-1-10

I keep getting an error everytime I run my code that says:

[out] = smallest_multiple(6) 
Error using gcd (line 23)
Inputs must be floats, namely single or double.
Error in smallest_multiple (line 4)
    out = (out * i) / (gcd(out,i));

Is 6 not a single?

Here is my code:

function [out] = smallest_multiple(n) 
out = uint64(1);
for i = 1 : n 
    out = (out * i) / (gcd(out,i));
end 
if out >= intmax('uint64')
    out = uint64(0); 
end 
end 

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Emma Sellers 2019-1-8

Thank you! I was usure of casting rules in matlab. I spent all of last semester on C programming and everything is running together.

Emma Sellers 2019-1-8

Also, I tried running a code similar to the link you provided (Because he said it worked up through 16) and I STILL got the same error I've been getting and it didn't run at all.

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采纳的回答

Jan 2019-1-8

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编辑：Jan 2019-1-8

Omit the explicit casting by uint64. Then Matlab uses the type double as default.

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Emma Sellers 2019-1-8

function [out] = smallest_multiple(n) 
out = uint64(1) ;
for i = 1 : n 
    y = (out * i) / (gcd(double(out),i));
    out = uint64(y);
end 
if out >= uint64(18446744073709551615)
    out = uint64(0); 
end 
end 

Emma Sellers 2019-1-10

So, yes it needs to work with larger numbers.. But heres the thing:

when I manually run the code with 45 in it (the number its failing on) I get this error:

[out] = smallest_multiple(45)
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
out =
  uint64
   0

But, it still puts out 0, which is what the question ask for.. So im confused as to why it doesn't work. I even tried pre programming it to whenever n is greater than 41 it equals 0. Because thats when it exceeds the uint64 bounds.

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更多回答（2 个）

Rik 2019-1-8

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There is an important difference between a single value (called a scalar in Matlab), and a value of data type single (which is an array that is stored in a specific format internally).

The gcd function requires the input to be a double or a single, so you should either keep it as a single/double or force it to be one, either with the cast function or by executing double(out).

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Rik 2019-1-9

Glad to hear you found a solution.

Do you need your code to work until a larger value? You might need to rework your algorithm. Another method of solving this question might be to check the prime factors and use ismember.

Emma Sellers 2019-1-10

So, yes it needs to work with larger numbers.. But heres the thing:

when I manually run the code with 45 in it (the number its failing on) I get this error:

[out] = smallest_multiple(45)
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
out =
  uint64
   0

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Emma Sellers 2019-1-10

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/438796-2520-is-the-smallest-number-that-can-be-divided-by-each-of-the-numbers-from-1-to-10-without-any-rema#answer_355874

So, yes it needs to work with larger numbers.. But heres the thing:

when I manually run the code with 45 in it (the number its failing on) I get this error:

[out] = smallest_multiple(45)
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
Warning: Inputs contain values larger than the largest consecutive flint.
         Result may be inaccurate. 
> In gcd (line 64)
  In smallest_multiple (line 6) 
out =
  uint64
   0

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Emma Sellers 2019-1-10

My code is at the very top of this feed. When I run the code like this:

[out] = smallest_multiple(45)
out =
  uint64
   409927646082434480

Thats what I get, but the grader STILL says it wrong cries*** ive been trying to figure this out for days.

Steven Lord 2019-1-10

That answer is not correct. There are several ways to see this. The first is to try the division.

x = uint64(409927646082434480)
d = x/3;
d2 = 3*d;
check = [x; d2]

If x were divisible by 3, the two elements in check would be the same. They aren't.

The sum of the digits in x is 80, which is another sign the answer is incorrect. The divisibility rule for 3 is that the sum of the digits must itself be a multiple of 3.

A third check is that the result must be divisible by both 25 (=5^2) and 4 = (2^2) so it must be a multiple of 100 (=2^2 * 5^2).

At this point, I think you've done your due diligence and should probably talk to your professor or teaching assistant. Do they expect you to do the calculations symbolically and check afterward if it's too large to fit in a 64-bit integer? Do they expect you to perform the calculations iteratively and stop as soon as the next one would saturate? It's not quite clear from the snippet of the assignment in the title of this post.

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