[C++] String Reversion using Pointers!

[C++] String Reversion using Pointers! - Printable Version

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[C++] String Reversion using Pointers! - Iyyel - 06-07-2015

Hello there guys!

So a little introduction about myself before I start to show you anything. I have been doing Java (on & off) for a few years now, and I recently started discovering the world of C++, and I must say I love it a lot. So here I am with a little tutorial/showcase on how to reverse a string or array of characters in C++ by the use of pointers.

Code:
#include <iostream>

int main(int argc, char *argv[])
{
    char text_array[] = "Hello!";

    int text_array_len = (sizeof(text_array) - 1);
    std::cout << "Char Array Len: " << text_array_len << std::endl;

    char *p_start = &text_array[0];
    std::cout << "Array Start: " << *p_start << std::endl;

    char *p_end = (text_array + text_array_len) - 1;
    std::cout << "Array End: " << *p_end << std::endl;

    std::cout << "Before: " << text_array << std::endl;

    while (p_start < p_end)
    {
        char save = *p_start;
        *p_start = *p_end;
        *p_end = save;

         p_start++;
         p_end--;
    }  

    std::cout << "After : " <<  text_array << std::endl;

    return 0;
}

A little explanation for my code. I take two integer pointers, pointing to the start character and end character of the array, as well as an integer that stores the length of characters in the array. I then use a while loop (you can use a for loop as well, this is just how I do it) to iterate through the array, essentially swapping the individual characters with each other.

Code:
Char Array Len: 6
Array Start: H
Array End: !
Before: Hello!
After : !olleH

And this is the output! As I said before, this is just how I do it. It works with single characters such as 'a' or 'b' as well with long arrays of characters. I hope this will be useful for at least someone!

Thanks for reading!

Iyyel.

RE: [C++] String Reversion using Pointers! - CoolixHD - 06-07-2015

Very nice tutorial, Iyyel! Keep up the good work. Smile

RE: [C++] String Reversion using Pointers! - Zodiac - 06-07-2015

Thanks for sharing this mate! Smile

RE: [C++] String Reversion using Pointers! - bitm0de - 07-29-2015

Here's my version:

Code:
char *reverse_string(char *src)
{
  if (!src || !*src) return src;
  char *p_beg = src;
  char *p = src;
  while (*(p + 1)) ++p;
  while (p > p_beg)
  {
    char tmp = *p;
    *p-- = *p_beg;
    *p_beg++ = tmp;
  }
  return src;
}

And just so you know, this is not the C++ way of going about reversing a string. C++ programmers rarely use (raw) pointers, and you would probably see an implementation using std: Confused

tring and iterators instead of pointers.