Reversing String logic

[M3GAPL3X]

I don't really understand what I am doing wrong with this function...basically what I want it to do is reverse a string (character by character).

Here is what I have so far:

void strReverse(char strng[])
{
	int i = 0, n, j=0;
	char reverse[80]; //the string that will reverse everything
	
	while (strng[i]) //while string isn't a null character '\0'
	i++; //increment i and store in string

	strng[i] = '\0';

	cout << strng << endl;
	
	n = strlen(strng); //find the length of the string after
	

	for (i=0; i < n; i++)
		for (j = n; j >= 0; j--)
		reverse[i] = strng[j];
		//i--;

	
	
	cout << "The reversed string is: " << reverse << endl;
}

Any help would be greatly appreciated.

[joe_bruin]

this code does nothing. why is it there?

Originally posted by M3GAPL3X

	while (strng[i]) //while string isn't a null character '\0'
	i++; //increment i and store in string

	strng[i] = '\0';

the inner loop shouldn't be there. think about how the characters will be copied. strng[0] -> reverse[n - 1], strng[1] -> reverse[n - 2] and so on. you only need one loop for this.
also, remember to put the '\0' at the end of 'reverse'.

	n = strlen(strng); //find the length of the string after
	

	for (i=0; i < n; i++)
		for (j = n; j >= 0; j--)
		reverse[i] = strng[j];
		//i--;

[Valmont]

// StrReversse.cpp : Entry point for this console app.
//Reversing a string.

/*The one and only core function swaps the first and last element of a char[], 
then it swaps the second element with the second last element. Etc.*/

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

//Reversing a string

//Forward declaration.
void reverse(char* s);

int main(int argc, char* argv[])
{
	cout<<"enter a sentence"<<endl;
	char szSentence[100];
	cin.getline(szSentence,100);

	reverse(szSentence);
	cout<< "Reversed string: "<<szSentence<<endl;

	return 0;
}

void reverse(char* s)
{
	char temp; //help variable for "swapping" 2 characters.

	int lenght = strlen(s);
	int lastchar = lenght - 1;

	for(int i=0;i<lenght/2; i++)
	{
		temp=s[i];
		s[i]=s[lastchar-i];
		s[lastchar-i]=temp;
	}

}

[joe_bruin]

Originally posted by Valmont

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

what could a commandline string reverse program possibly need 'stdafx' for?

[Valmont]

I made this proggy on the fly, habit wise.
The essence is nevertheless clear It hink .

[Unicorn]

Writing a function to reverse a string is a good way to get familiar with the language. In future projects however, you might want to use the reverse function from the standard C++ library:

#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

int main (int argc, char **argv)
{
  char sentence[100];
  cin.getline (sentence, 100);
  reverse (sentence, sentence + strlen (sentence));
  cout << sentence << endl;
  
  return 0;
}

[redhead]

What ISO describes the reverse() function ?? and when looking at the code, I can't seem to figure out, why the second argument should be: sentence + strlen (sentence) shouldn't this be something like strlen (sentence)

I would guess the first one, would return the string which gets the length of it appended in the end.. An argument I dont see any use for in any function.

[Valmont]

Don't worry about that. Just try to make own algorithms first.
At least learn things like strcpy. Then you'll move on .

[Unicorn]

Originally posted by redhead
What ISO describes the reverse() function ??

That would be ISO/IEC IS 14882.

... and when looking at the code, I can't seem to figure out, why the second argument should be: sentence + strlen (sentence) shouldn't this be something like strlen (sentence)

In most STL functions, a range is used instead of a starting point and a distance. So the first argument is the starting point, and the second argument should point right after the last element of the thing you want to reverse. (Remember "sentence" is the address of the first character.)