Problems With Reversing A String

[iccaros]

ok I'm having a problem with the following..

the varable CheckHolder is not putting anything out..

it should be a backwords output of LineToCheck and I put some Cout lines to see what it is during processing and it seams to work untill the last line I get blank for CheckHolder

#include<iostream>
#include <cctype>
#include <string>

using namespace std;

//function prototypes
//void clear_screen();
//void check(const char);

//main function
int main()
{
        //local varables
        char LineToCheck[255];
        char CheckHolder[255];
        int SizeOfChar=0, y = 0;
        string str;


        cout << "Enter string:" << endl;


        cin.get(LineToCheck,255);

                str = LineToCheck;
        SizeOfChar = str.length();
        cout << "you enterd " << SizeOfChar << " charaters" << endl;

        for (int x = SizeOfChar; x >= 0; x--)
        {
                CheckHolder[y] = LineToCheck[x];
                cout << "checkholder = " << CheckHolder[y] << endl;
                y++;

        }

   

        cout << " Line to check = " << LineToCheck<< endl;
        cout << "check holder = " << CheckHolder  << endl;
        return 0;
}

my output

bash-2.05b$ g++ extra.cpp
bash-2.05b$ ./a.out
Enter string:
This is a string
you enterd 16 charaters
checkholder =
checkholder = g
checkholder = n
checkholder = i
checkholder = r
checkholder = t
checkholder = s
checkholder =
checkholder = a
checkholder =
checkholder = s
checkholder = i
checkholder =
checkholder = s
checkholder = i
checkholder = h
checkholder = T
 Line to check = This is a string
check holder =
bash-2.05b$                  

[iccaros]

to add I can see the output of CheckHolder if I add a for loop

for (int x = 0; x <=  SizeOfChar; x++)
cout << CheckHolder[x];
cout << endl;

this is not the a good soultion as I must newt strip out any spaces and puntuation, then make everything lowercase for comparison..

I don't need these answers .. as I need to learn to do them and I can only learn with trial and error.. but this char problem is makeing me mad..

(do I need to read it into a string?)

[jcl]

The problem is that you're copying the entire string into CheckHolder reversed, including the terminating null character. The null char is inserted at CheckHolder[0], so CheckHolders ends up being a C string of length 0. You need to start copying from the last non-null character and then insert a null at the end of the reversed string.

It is a good idea to the use the string class whenever possible. C strings are a legacy feature.

Excursus: It's probably beyond the scope of your assignment, but C++ makes this fairly easy if you use more of the features of the standard library:

#include <iostream>
#include <string>

using namespace std;

int main()
{
    string in;

    cin >> in;
    cout << string(in.rbegin(), in.rend()) << endl;

    return 0;
}

Edited May 24, 2005 by jcl

[CurlingSteve]

"One Off" errors are very easy to fall into, especially when learning C.

A 16 character string for instance is typically looped with:

For (x=0;x<16;x++).

Beginners typically forget that C arrays are indexed starting at zero, so the scan goes to length - 1 (using the "<" test instead of "<=" is a common way to cover that).

And as JCL said, it's very easy to be caught by the terminating zero byte.

[iccaros]

The problem is that you're copying the entire string into CheckHolder reversed, including the terminating null character. The null char is inserted at CheckHolder[0], so CheckHolders ends up being a C string of length 0. You need to start copying from the last non-null character and then insert a null at the end of the reversed string.

It is a good idea to the use the string class whenever possible. C strings are a legacy feature.

Excursus: It's probably beyond the scope of your assignment, but C++ makes this fairly easy if you use more of the features of the standard library:

#include <iostream>
#include <string>

using namespace std;

int main()
{
    string in;

    cin >> in;
    cout << string(in.rbegin(), in.rend()) << endl;

    return 0;
}

jcl,

that captures the first word until the first space..

my problem with that is I need to capture and entire line.. strip out spaces, puctuation and case and see it its the same forwared as it is backwards.. the only ohte rrequirment is I must use cin.get();

so now the question.. if I put the input in to a Char first, then move everything but spaces and puncuation into the string I should be half way there right?

I am assuming this is putting out the string twice.. once forward (rbegin) and agian (rend)

I'll go look up the string class so I understand more..

thanks

[jcl]

that captures the first word until the first space..

Yeah. It was just supposed to incite interest in the standard library.

so now the question.. if I put the input in to a Char first, then move everything but spaces and puncuation into the string I should be half way there right?

Right. You can combine the editing and reversal in one loop if you wish.

Edited May 25, 2005 by jcl

[iccaros]

Yeah. It was just supposed to incite interest in the standard library

it did