printing a string backwards

[informrefer]

When I run this code, the same string that I entered is couted, except that I switch the first and last letters, the second-to-last and second letter, etc.

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

using namespace std;
const int Arsize = 30;

int main()
{
cout << "Enter a string\n";
char strine[Arsize];
cin.getline(strine, Arsize);
//for (int i = strlen(strine)-1; i>=0; i--)
//strine[i]='k';
for (int i = strlen(strine)-1, j=0; i>=((strlen(strine))/2); i--, j++)
strine[i], strine[j]=strine[j], strine[i];
for (int i = 0; i<=strlen(strine)-1; i++)
cout << strine[i];
return 0;
}

[Duthomhas]

Please use [code] tags -- it makes life so much easier for those who want to help you.

Line 15:

  for (int i = strlen(strine)-1, j=0; i>=((strlen(strine))/2); i--, j++)
    strine[i], strine[j]=strine[j], strine[i];

You are not changing anything. The comma isn't doing what you think it is. That is, you can only assign one thing at a time, not two, as in Python.

You'll have to have a temporary variable, assign strine[i] to it, copy j to i, then the temp to j.

Hope this helps.

[Garion]

Maybe use the .size() function to figure out how many characters are in the string.

http://www.cplusplus.com/reference/string/string/size/

Then loop through each element of the string printing it from last to first.

It could look something like this

std::string str = "Hello World";

for (unsigned int i = str.size() ; i > 0; i--){
   //code to print stuff
}

[Duthomhas]

...except he is using a c-string and not a std::string.

[Garion]

My mistake, just assumed it was C++ because, well the forum heh.

You could make a loop to count the size of the c-string. The logic of the loop above would remain the same.



Maybe something like this (my understanding is a c-string is just a regular c++ string with a null character at the end)

int c_str_size = 0;
std::string str "Hello World\0" //or however else you have your c-string set up

for (int i = 0; str[i] != '\0'; i++){
      c_str_size++;
     }

for (int i = c_str_size - 1 ; i > 0; i--){//skip the first null character if you want or print it and remove -1
   //code to print stuff
}

basically just derive the .size() function for your own usage.

[Chervil]

You could make a loop to count the size of the c-string.

Other than as an educational exercise, there's no point in reinventing the wheel. The strlen() function is already in the library and fulfils the requirement.
http://www.cplusplus.com/reference/cstring/strlen/

[Garion]

Good info there Chervil :)

I haven't really messed with cstrings all that much. Sometimes I find it overwhelming to look through all the libraries and end up making functions myself lol. It's probably not the best way to go about it xD