about product in uint64

Question

Nguyen Huy 2021-5-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/833898-about-product-in-uint64

编辑： Jan 2021-5-20

My question is iven an integer x which contains d digits, find the value of n (n > 1) such that the last d digits of x^n is equal to x. If the last d digits will never equal x, return inf.

Example :

%x = 2; (therefore d = 1)
%2^2 = 4, 2^3 = 8, 2^4 = 16, 2^5 = 32
%n = 5;

So my solution is take x into uint64 vecto,then take the x^n by take product of a*x with example is

a=uint64([x])
for i=1:inf
a=a*x
for j=length(a):-1:1
     b=rem(a(j)/10)
     c=mod(a(j),10)
     if a(j)>10
     a(j)=c
     a(j-1)=a(j-1)+b
end
end
if x==a(end-d:end)
break
end
end

%example : 0 0 0 2 *

2

==========

0 0 0 4 => [0 0 0 4]*2 =>[0 0 0 8]*2=>[0 0 0 16]=[0 0 1 6]*2=>[0 0 0 32]=[0 0 3 2] have a(end-d:end)==x then break

so my question is how could i product the number with over 2 digits in uint64()

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jan 2021-5-20

Why do you use uint64 instead of uint8 to store decimal digits?

What about limiting the solution to the UINT64 range, which is at least up to 1.8e19?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2021-5-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/833898-about-product-in-uint64#answer_704378

编辑：Jan 2021-5-20

在 MATLAB Online 中打开

With limiting the values to UINT64 range:

x   = uint64(2);
d10 = uint64(10^(floor(log10(x)) + 1));
n   = 2;
a   = x^n;
lim = intmax('uint64');
while rem(a, d10) ~= x && a <= lim
   a = a * x;
   n = n + 1;
end
if a < lim
    disp(n)
else
    disp('search failed.');
end