Programming Forums > Application Development > C++

biohazard · Mar 14th, 2006, 11:46 PM

i tried to reverse a string using arrays and for loops i the following program
[code]
#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
int i,j;
cout<<"enter the array";
char arr[10],rr1[10];
for(i=0;i<10;i++)
cin>>arr[i];
for(i=9;i>=0;i--)
for(j=0;j<=9;j++)
rr1[j]=arr[i];
for(j=0;j<=9;j++)
cout<<rr1[j];
system("pause");
return 0;
}
[code]
the reversed array is assigned 9 elements which are equal to the first element of arr.

bivhitscar · Mar 15th, 2006, 12:08 AM

(Toggle Plain Text)

#include<iostream>
#include<cstdlib>
using namespace std;

int main()
{
int i,j;
cout<<"enter the array";

char arr[10],rr1[10];

for(i=0;i<10;i++)
cin>>arr[i];

for(i=9;i>=0;i--)
{
for(j=0;j<=9;j++)
rr1[j]=arr[i];
}

for(j=0;j<=9;j++)
cout<<rr1[j];

system("pause");
return 0;
}

I have only done C, but I assume you need the braces around that for loop in C++ as well.

And you don't actually have to use two arrays to complete this task either.

AICkieran · Mar 15th, 2006, 12:48 AM

This should help, i code in C, I dont know much c++ but it should work

[PHP]
#include <stdio.h>
#include <string.h>

int main()
{
char name[]="kieran";
int len=strlen(name)-1;
int i=0;

while(i<len)
{
name[i]^=name[len];
name[len]^=name[i];
name[i]^=name[len];

++i; --len;
}

printf("%s\n", name);

return 0;
}
[/PHP]

:banana:

InfoGeek · Mar 15th, 2006, 1:38 AM

(Toggle Plain Text)

        name[i]^=name[len];
        name[len]^=name[i];
        name[i]^=name[len];

Why use ^ operator just to save a temporary variable?
do this instead:

(Toggle Plain Text)

        char temp=name[len];
        name[len]=name[i];
        name[i]=temp;

The Dark · Mar 15th, 2006, 2:57 AM

@biohazard: In your original code, you have this loop (reindented):

(Toggle Plain Text)

  for(i=9;i>=0;i--)
    for(j=0;j<=9;j++)
      rr1[j]=arr[i];

The inner for loop (on j) is performed for each iteration of the outer loop (on i). The inner for loop is setting all values of the rr1 array to the value of arr[i]. This means that in the end all values of rr1 are going to be equal to arr[0] (as that is the last value of i used).
You don't need the inner loop, you just want to copy the value from the arr array to its reversed position in the rr1 array

(Toggle Plain Text)

  for(i=9;i>=0;i--)
    rr1[9-i]=arr[i];

@bivhitscar: you don't need braces around those for loops as they are only one statement. I would normally put braces there for clarity, but it is not required.

CodeWeasel · Mar 15th, 2006, 3:25 AM

(Toggle Plain Text)

void reverseString( char* in, char* out )
{
	int inLength = strlen( in );
	if( strlen( out ) >= inLength )
	{
		out[inLength] = '\0';
		for( int i = inLength-1; i > -1; i-- )
			out[i] = *in++;
	}
}

Only stipulation with using this code is that you should back up the original string if you want to use it again.

bl00dninja · Mar 18th, 2006, 1:34 AM

Quote:

#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
int i,j;
cout<<"enter the array";
char arr[10],rr1[10];
for(i=0;i<10;i++)
cin>>arr[i];
for(i=9;i>=0;i--)
for(j=0;j<=9;j++)
rr1[j]=arr[i];
for(j=0;j<=9;j++)
cout<<rr1[j];
system("pause");
return 0;
}

jucgbrshfrshf387yto8p42389r7234b9rpyr7yoc87y23l7yf7iofhnwerhfh4roifh45w
2icgnyoi5hygfco8hyfbo857bcn37hfcw53o7fhbc357h357nfhc35t
cg2589yu598y87fyb5c487fyh5o7fc5nhc85f8x45nh8x7f75h2
fcx2unx9825u98235y98fcy3b278f23rxyf7fh845n8743hyfc8w3yfrrsdjsegmufye

Nebula · Mar 18th, 2006, 1:40 AM

Quote:

Quote:
#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
int i,j;
cout<<"enter the array";
char arr[10],rr1[10];
for(i=0;i<10;i++)
cin>>arr[i];
for(i=9;i>=0;i--)
for(j=0;j<=9;j++)
rr1[j]=arr[i];
for(j=0;j<=9;j++)
cout<<rr1[j];
system("pause");
return 0;
}

jucgbrshfrshf387yto8p42389r7234b9rpyr7yoc87y23l7yf 7iofhnwerhfh4roifh45w
2icgnyoi5hygfco8hyfbo857bcn37hfcw53o7fhbc357h357nf hc35t
cg2589yu598y87fyb5c487fyh5o7fc5nhc85f8x45nh8x7f75h 2
fcx2unx9825u98235y98fcy3b278f23rxyf7fh845n8743hyfc 8w3yfrrsdjsegmufye

Point made.

biohazard · Mar 18th, 2006, 8:50 AM

i didnt get u blood ninja.
do you mean that it prints a load of junk values

Nebula · Mar 18th, 2006, 11:30 AM

Use code marks, It's ALOT easier to read and understand the code. Aspecially for those who are helping you with it.

Mar 14th, 2006, 11:46 PM	#1
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	reversing a string i tried to reverse a string using arrays and for loops i the following program [code] #include<iostream> #include<cstdlib> using namespace std; int main() { int i,j; cout<<"enter the array"; char arr[10],rr1[10]; for(i=0;i<10;i++) cin>>arr[i]; for(i=9;i>=0;i--) for(j=0;j<=9;j++) rr1[j]=arr[i]; for(j=0;j<=9;j++) cout<<rr1[j]; system("pause"); return 0; } [code] the reversed array is assigned 9 elements which are equal to the first element of arr.

Mar 15th, 2006, 12:08 AM	#2
bivhitscar Hobbyist Programmer Join Date: Oct 2005 Location: Melbourne, Australia Posts: 126 Rep Power: 4	(Toggle Plain Text) #include<iostream> #include<cstdlib> using namespace std; int main() { int i,j; cout<<"enter the array"; char arr[10],rr1[10]; for(i=0;i<10;i++) cin>>arr[i]; for(i=9;i>=0;i--) { for(j=0;j<=9;j++) rr1[j]=arr[i]; } for(j=0;j<=9;j++) cout<<rr1[j]; system("pause"); return 0; } #include<iostream> #include<cstdlib> using namespace std; int main() { int i,j; cout<<"enter the array"; char arr[10],rr1[10]; for(i=0;i<10;i++) cin>>arr[i]; for(i=9;i>=0;i--) { for(j=0;j<=9;j++) rr1[j]=arr[i]; } for(j=0;j<=9;j++) cout<<rr1[j]; system("pause"); return 0; } I have only done C, but I assume you need the braces around that for loop in C++ as well. And you don't actually have to use two arrays to complete this task either. __________________ it's ironic considerate rarity patron of love higher knowledge engulfs me...

Mar 15th, 2006, 1:38 AM	#4
InfoGeek Professional Programmer Join Date: Jun 2005 Location: India, The great. Posts: 435 Rep Power: 4	(Toggle Plain Text) name[i]^=name[len]; name[len]^=name[i]; name[i]^=name[len]; name[i]^=name[len]; name[len]^=name[i]; name[i]^=name[len]; Why use ^ operator just to save a temporary variable? do this instead: (Toggle Plain Text) char temp=name[len]; name[len]=name[i]; name[i]=temp; char temp=name[len]; name[len]=name[i]; name[i]=temp; __________________ PFO - My daily dose of technology.

Mar 15th, 2006, 2:57 AM	#5
The Dark Expert Programmer Join Date: Jun 2005 Posts: 894 Rep Power: 4	@biohazard: In your original code, you have this loop (reindented): (Toggle Plain Text) for(i=9;i>=0;i--) for(j=0;j<=9;j++) rr1[j]=arr[i]; for(i=9;i>=0;i--) for(j=0;j<=9;j++) rr1[j]=arr[i]; The inner for loop (on j) is performed for each iteration of the outer loop (on i). The inner for loop is setting all values of the rr1 array to the value of arr[i]. This means that in the end all values of rr1 are going to be equal to arr[0] (as that is the last value of i used). You don't need the inner loop, you just want to copy the value from the arr array to its reversed position in the rr1 array (Toggle Plain Text) for(i=9;i>=0;i--) rr1[9-i]=arr[i]; for(i=9;i>=0;i--) rr1[9-i]=arr[i]; @bivhitscar: you don't need braces around those for loops as they are only one statement. I would normally put braces there for clarity, but it is not required.

Mar 15th, 2006, 3:25 AM	#6
CodeWeasel Newbie Join Date: Jul 2004 Location: Blacksburg, VA Posts: 13 Rep Power: 0	(Toggle Plain Text) void reverseString( char* in, char* out ) { int inLength = strlen( in ); if( strlen( out ) >= inLength ) { out[inLength] = '\0'; for( int i = inLength-1; i > -1; i-- ) out[i] = in++; } } void reverseString( char in, char* out ) { int inLength = strlen( in ); if( strlen( out ) >= inLength ) { out[inLength] = '\0'; for( int i = inLength-1; i > -1; i-- ) out[i] = *in++; } } Only stipulation with using this code is that you should back up the original string if you want to use it again.

Mar 15th, 2006, 12:48 AM	#3
AICkieran Programmer Join Date: Jan 2006 Location: UK Posts: 55 Rep Power: 3	This should help, i code in C, I dont know much c++ but it should work [PHP] #include <stdio.h> #include <string.h> int main() { char name[]="kieran"; int len=strlen(name)-1; int i=0; while(i<len) { name[i]^=name[len]; name[len]^=name[i]; name[i]^=name[len]; ++i; --len; } printf("%s\n", name); return 0; } [/PHP] :banana:

Mar 18th, 2006, 8:50 AM	#9
biohazard Newbie Join Date: Feb 2006 Posts: 18 Rep Power: 0	i didnt get u blood ninja i didnt get u blood ninja. do you mean that it prints a load of junk values

Mar 18th, 2006, 11:30 AM	#10
Nebula Hobbyist Programmer Join Date: Oct 2005 Posts: 205 Rep Power: 4	Use code marks, It's ALOT easier to read and understand the code. Aspecially for those who are helping you with it. __________________ When will Jesus bring the porkchops?

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Programming Forums > Application Development > C++

reversing a string