Reversing a String

I'm trying to write a function that will return the reverse of a character array or string. Here's how I want everything to work out:

1). The user is asked for a string/character array.
2). The user enters a string/character array (the size is unknown until the user enters the string/character array, so I'm not sure how to set up the memory allocation).
3). The function reads the string/character array and reverses it. So if the user enters, "this is my test" the function will return "tset ym si siht".

I can't figure out any way to do this other than to create a string or character array and copy one letter at a time from the user input into the reversed string/character array. Unfortunately, I can't seem to figure out how to copy a single character from one string into another.

Here's the code I have so far:

******************************************

string ReverseString(string input){

int length = input.length();

string rString = "\0";

for(int i = 0; i<length; i++)
// CODE HERE THAT WILL
// COPY ONE CHARACTER FROM
// INPUT INTO rString

return rString;

}

******************************************

Thanks in advance!

If you want to add to a string all you have to do is use the += operator eg

string name = "z";
name +="e";
name +="n";

Code:

---

#include <iostream>
#include <string>

using namespace std;

// swaps given two characters
void swap(char& a, char& b) {
    char temp = a;
    a = b;
    b = temp;
}

/* reverses string by swapping first character with last character
 * second character with second to last character, third character with
 * third to last character, etc. 
 */
string reverse(string source) {
    int len = source.length();
    int count;
   
    for (count = 0; count < len/2; count++) {
        swap(source[count], source[len-count-1]);
    }
    return source;
}

/* tests string reversal by outputting string before reversing it,
 * reversing the string and outputting the reversed string, and then
 * reversing it again to see if the twice reversed string is the same as
 * the original
 */
bool test(string& testString) {
    string copy = reverse(testString);
    cout << "String before reversing: " << testString<< "\n";   
    cout << "String after reversing : " << copy << "\n";
   
    copy = reverse(copy);
   
    if ( copy == testString) {
        cout << "It may have worked" << endl;
        return true;
    }
    else {
          cout << "It did not work" << endl;
          return false;
    }
}

// calls test for an array of strings
int main(int argc, char *argv[])
{
    string testStringArray[] = {"Rob", "Words", "SilentStrikeIsHelpingYouOut",
    "radar", "five"};
   
    // ugly way of finding out how many strings are in array, but will work if
    // more strings are added to the array
    int arrayLen = sizeof testStringArray / sizeof testStringArray[0]; 
   
    int count;
    for (count = 0; count < arrayLen; count++) {
        test(testStringArray[count]);
    }
   
    char wait; cin >> wait;
  return 0;
}

---

Gah... those code tags don't seem to work.

If you made this a vector you could easily avoid this

Quote:

---

Originally posted by SilentStrike

If you made this a vector you could easily avoid this

// ugly way of finding out how many strings are in array, but will work if
// more strings are added to the array
int arrayLen = sizeof testStringArray / sizeof testStringArray[0];


[/B]

---

That is a specific instance in which the easy method to define all the data in the array is worth the lack of all features of a vector.

his code isnt so critical that he needs to use an array either, i just prefer vectors because if i ever need to use an algorithm on them it's already compatible.


anyway i just remembered there is a reverse algorithm defined by the STL.. i can't find how it works right now though so i don't know if it'd be useful

I prefer usually vectors as well.. but that was a rare case in which I think it's better to just use an array.

string testStringArray[] = {"Rob", "Words", "SilentStrikeIsHelpingYouOut",
"radar", "five"};

int arrayLen = sizeof testStringArray / sizeof testStringArray[0];

is more readable than

vector<string> testStringArray;
testStringArray.push_back("Rob");
testStringArray.push_back("Words");
testStringArray.push_back("SilentStrikeIsHelpingYo uOut");
testStringArray.push_back("radar");
testStringArray.push_back("five");

int arrayLen = testStringArray.size();

true, i'm just trying to open some peoples eyes to vectors.

>>anyway i just remembered there is a reverse algorithm defined by the STL.. i can't find how it works right now though so i don't know if it'd >>be useful


Like this -


#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int main ()
{
string name = "zen";

string::iterator start=name.begin();
string::iterator end=name.end();

reverse(start,end);

cout << name<<endl;

return 0;

}

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

void main()
{
char ass[255];

cin.getline(ass, 255, '\n');
cout<<"String before reverse: "<< ass<<"\n";
strrev(ass);
cout<<"String after reverse: "<<ass<<"\n";
}