radix (numeral systems)

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This is my question:
Find all natural numbers not exceeding a given m, the binary notation which is a symmetrical sequence nudey and ones (starting from one). Show decimal and binary records of these numbers.

I am new to programming in C++. I've been trying to solve this question but haven't been successful.

int m;
cout<<"Enter the starting number: ";
cin>>m;

while(m>0)
{
  cout<<m<<"   ";
  --m;
}

This gave me what i needed.

Now I need to get the binary form of these numbers and show out the ones that are symmetrical.
i.e for example 1001.
After which the ones that fall into the category will be changed back decimal and shown on the monitor.

I will be very grateful if some could help me out.
Thank you in anticipation for your response.

Posted 2-Sep-12 15:24pm

karochi123

Updated 3-Sep-12 2:04am

Joan M

v3

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pasztorpisti 2-Sep-12 21:33pm

And what have you tried so far? What is the first obstacle you couldn't get over?

karochi123 2-Sep-12 21:59pm

my first obstacle was creating a function that detect the symmetrical numbers. The symmetrical numbers are to be in binary form and are to start with '1' and end with '1'. for example 1001.

pasztorpisti 3-Sep-12 3:16am

Depending on the maximum value of m you might not want to detect but construct a symmetric value.

[no name] 2-Sep-12 21:37pm

Did your teacher happen to mention what "symmetrical sequence nudey" is supposed to mean?

pasztorpisti 2-Sep-12 21:40pm

Tried to search for nudey in a dictionary and with google but all I found was "nudey beach" :-) I guess it has something to do with the trailing zeros in the binary representation...

karochi123 2-Sep-12 22:09pm

nudey is just zero.

karochi123 2-Sep-12 22:04pm

yes.

step 1. Give in a number.
step 2. all natural numbers less than or even to the given number.
step 3. The binary form of the numbers
step 4. "Now the symmetry"for example, 1001 is a symmetrical number.
step 5. show out all the numbers that fall into that category on the monitor.

[no name] 2-Sep-12 22:14pm

Okay... so.... how far have you gotten so far? "haven't been successful" does not tell us anything about what you have tried or where you are stuck or even tell us what your question even is. Sounds like you know what it is that you have to do so it's just a matter of reading your textbook and doing your homework.

karochi123 2-Sep-12 22:18pm

am stuck at step 4. I've been on it since yesterday(

karochi123 2-Sep-12 22:04pm

yes. step 1. Give in a number. step 2. all natural numbers less than or even to the given number. step 3. The binary form of the numbers step 4. "Now the symmetry"for example, 1001 is a symmetrical number. step 5. show out all the numbers that fall into that category on the monitor.

pasztorpisti 2-Sep-12 21:48pm

You should ask for a sample output for a reasonably small m, for example 10 or 20. It is also useful to know the largest possible m value for many reasons.

karochi123 2-Sep-12 22:07pm

yeah. I've been working on it since yesterday. My major problem is writing out a function that will convert the numbers from decimal to binary and check if the binary number starts with one and ends with one.

pasztorpisti 3-Sep-12 3:14am

This is not an answer the my questions, for example if 010 is symmetric or not. You have to know if prefix/postfix zeros are allowed or not. And what about the maximum value of m? These will be important parameters for you to solve the problem!

Joan M 3-Sep-12 1:56am

We won't do your homework.
You should do it to learn to solve problems that the day you will work you will have to solve.
We are helping people though...

So ho does CP works?

We like to get specific questions: i.e. I've read this documentation (link) and after trying (code) I've seen that this is not working as I expected as the output is this one (output) and I would like to get this one (output).

If you do that (read posting guidelines) you'll get answers. If you don't do that... well, you'll get downvotes and fired from CP...

PS: don't repost, we hate that. If you want to add more details into your question, then use the "Improve question" green link under your question itself.

Good luck.

karochi123 3-Sep-12 7:11am

Of course i don't expect you to solve my homework. I got out of ideas...
Thank you for your advice.

Joan M 3-Sep-12 7:28am

Then you should tell us what you've tried, what has failed and what you want to solve in your code... if you've thought on the issue, then knowing what you've thought will help us to avoid spending time thinking in the same.

karochi123 3-Sep-12 7:38am

The question is very interesting. this is what i did:
int m;
cout<<"Enter the starting number: ";
cin>>m;

while(m>0){
cout<<m<<" ";
--m;}
This gave me what i needed. Now i need to get the binary form of these numbers and show out the ones that are symmetrical. i.e for example 1001. After which the ones that fall into the category will be changed back decimal and shown on the monitor.

Joan M 3-Sep-12 8:05am

That's what we require always, look, I've improved your question by adding your complete comment: a code block and the extra bits of explanation there. I'm sure someone will give you good pointers on how to solve that...

Humberto 3-Sep-12 7:04am

Isn't this the same problem as finding all odd numbers less then m?

Stefan_Lang 3-Sep-12 11:00am

Not so: 1011 (the decimal number 11) is odd, but not symmetric. It is however true that all symmetric numbers must be odd, assuming there are no leading zeros: since all binary numbers start with a 1, a symmetric binary must also finish with a 1.

karochi123 3-Sep-12 13:49pm

Thank you so much for the explanation. I wouldn't have explained any better. For me, the most interesting part of the program is writing the function that detects the symmetric numbers and shows them out.

Humberto 5-Sep-12 12:56pm

You are right, sir!
If am not wrong the OP wants to find all binary palindromes less then m. If so, a search for "how to find binary palindrome" can help.

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Philip Stuyck · Accepted Answer · 2012-09-02T21:19:00

Check out the following api's for easy converting to binary and to strings :

http://www.cplusplus.com/reference/clibrary/cstdlib/itoa/[^]

http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/[^]

Now how go about this :
- user enters a number, this number is the maximum number, you only want numbers that are binary symetrical below that number.
- now you need a loop where you will start with say i and initialise it to 1
- convert i to a binary string using above api
- copy the result binary string in another string, this string must be big
- keep appending to this string from the first binary string, but from the back of the string to the beginning. You now have a symetrical string
- convert it to a number.
- if the number is bigger than what the user enters, loop should stop, otherwise print the number and binary representation.

This should get you started with enough information to get the job done I think.

Stefan_Lang · Accepted Answer · 2012-09-03T05:12:00

Solution 2

Starting from the string of the binary number (which you said you have), create two pointers pointing to (1) the start of the binary string and (2) the last character of that same string. Make a loop, and inside that loop compare the characters the two pointers are pointing to, then move the first pointer to the next, and the end pointer to the previous character. Repeat until either you find a mismatch, or the first pointer moves past the end pointer.

Note, when I say pointer, nothing stops you from using a std::string and iterators instead. In that case however comparing the iterators may be tricky (feel free to ask again if you can't solve it)

Posted 3-Sep-12 5:12am

Stefan_Lang

Comments

karochi123 9-Sep-12 12:29pm

#include "stdafx.h"
#include <iostream>
#include <math.h>

using std::cout;
using std::cin;
using std::endl;

int _tmain(int argc, _TCHAR* argv[])
{

int m;
cout<<"Enter a number: ";
cin>>m;

while (m>0)
{
cout<<m<<" ";

int num, rem, i =1, total = 0;
num = m;

do

{
rem=num%2;
total=total +(i*rem);
num/=2;
i=i*10;

}
while (num>0);
cout<<total<<endl;
--m;
}

return 0;
}

This is what i have been able to do. how do i use the pointers now to compare and finish up the project?

Stefan_Lang 10-Sep-12 5:57am

You should try and fix your code first:
1. there are numerous opening and closing braces missing
2. there is no variable to hold the result, or at least no variable of a proper type for that purpose (array of char or std::string)
3. You are mixing base 10 and base 2 conversion in the two lines

num/=2;
i=i*10;

You are suffering from attention splitting: you have all the things you wish to do in your head and try to solve it all at the same time. As a result your code mixes up parts of the solutions, resulting in a jumble of code that is hard to follow, understand, and fix.

I suggest you split up the individual steps into functions. That will allow you to better focus on each step without distraction. It will also result in a better code structure.

Start with this:

#include <io>
int requestNumber() {
   // request and read a number from standard input
   int result = 0;
   // ask for input, read, and check that it's ok
   // ...

   return result;
}
std::string convertToBinary(int m) {
   // convert a number into a binary string representation
   std::string result;
   // iterate over the bits of m and store them as '1' and '0' in result
   // ...

   return result;
}
bool checkPalindrome(std::string str) {
   // test a string for being a palindrome
   return result = true;
   // iterate over string until you find a non-symmetric part, or you are done
   // ...

   return result;
}
int _tmain(int c, TCHAR* v[]) {
   int result = 0;
   // call each function and print intermediate results
   // ...

   return result;
}

Another hint: compile and run this regularly, to make sure you have no syntax errors, and to check at which step of the program your code fails to deliver the expected results.

You may notice that I defined a 'result' variable in each and every function and initialized it to some value. It is a practice I keep for various reasons, but mostly because it's very easy to recognize as the variable for storing a functions' final result. Also, it's easy to check whether a function result is equal to its initial value when you know that it's always initialized in the first line of any function.