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How to reverse a number

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sss dzu
sss dzu on 1 Dec 2012
Commented: Walter Roberson on 6 Sep 2022
Hi, I want to reverse a number, not a vector, like 8549 to 9458. I used fliplr , or flipud, or y = x(end:-1:1), They just work for row vector. Please, help. Thank you

Answers (8)

Azzi Abdelmalek
Azzi Abdelmalek on 1 Dec 2012
Edited: Azzi Abdelmalek on 1 Dec 2012
a=8549
out=str2num(fliplr(num2str(a)))

Roger Stafford
Roger Stafford on 21 Nov 2014
@Jessica: Let x be a non-negative integer. Then y will have the decimal digits of x in reversed order.
y = 0;
while x > 0
t = mod(x,10);
y = 10*y+t;
x = (x-t)/10;
end
  2 Comments
Kunal  Kabi
Kunal Kabi on 8 Jun 2017
Thank you sir because of you i got the idea @RogerStafford.
ABHAS BHATIA
ABHAS BHATIA on 14 Jan 2018
Thanks for the solution @Jessica

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Kunal  Kabi
Kunal Kabi on 8 Jun 2017
Edited: Jan on 28 Aug 2019
If you want to find palindrome numbers between two range here is the answer
clc;
clear all;
close all;
num=input('Enter first range:');
num1=input('Enter second range:');
for i=num:num1
temp=i;
reverse=0;
while temp > 0
t = mod(temp,10);
reverse = 10*reverse+t;
temp = (temp-t)/10;
end
if i==reverse
fprintf('Number is palindrome. %d\n',reverse);
end
end

Jan
Jan on 14 Jan 2018
Edited: Jan on 14 Jan 2018
A vectorized version of Roger's method:
n = 8549;
d = 10 .^ (0:floor(log10(n))); % [1 10, 100, 1000]
v = rem(floor(n ./ d), 10); % The vector of digits
r = v * flip(d).' % Vector multiplication with [1000, 100, 10, 1]

José-Luis
José-Luis on 1 Dec 2012
A vectorized, faster alternative
For integers:
your_answer = flipud(sscanf(fliplr(sprintf('%d ',a)),'%d '));
And floating point:
your_answer = flipud(sscanf(fliplr(sprintf('%f ',a)),'%f '));
Example:
a=randi(115422,10000,1);
your_val = flipud(sscanf(fliplr(sprintf('%d ',a)),'%d '));

Jessica
Jessica on 21 Nov 2014
what if you aren't allowed to use any string variables, string related function, digitrevorder() and fliplr()??
  1 Comment
Andrew Reibold
Andrew Reibold on 21 Nov 2014
Then you can do divide by 10 tricks with rounding to save each digit, then rearrange after.

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Kunal  Kabi
Kunal Kabi on 8 Jun 2017
Here is your answer
clc;
clear all;
close all;
num=input('Enter a number:');
num1=num;
reverse=0;
while num1 > 0
t = mod(num1,10);
reverse = 10*reverse+t;
num1 = (num1-t)/10;
end
reverse
num
if num==reverse
disp('Number is palindrome.');
else
disp('Number is not palindrome');
end

ANIRUDDHA
ANIRUDDHA on 6 Sep 2022
  1. Using function statement, find out the sum of the inverse of any two numbers, a, b. Choose any value of a and b to run program?
  1 Comment
Walter Roberson
Walter Roberson on 6 Sep 2022
This does not appear to be an answer to the question that was asked.

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