reverse of the string using recursion

Question

Hey guys i get stuck in the unusual situation. This is my code, it works perfectly for returning the reverse of the string but it gives output with including the space so I don't want that space to be included in my programme output so anyone has suggestions about this plz share it... by the way this is my code :

#include <iostream>

using namespace std;

string reverse(string str, int size) {
  if (size == -1)
    return "";
  else
    {
      char a;
      a = str[size];
      return a + reverse(str, size - 1);
    }
}

int main() {
  int size;
  cout << "the size of the string : ";
  cin >> size;
  string str;
  cout << "enter the word : ";
  cin >> str;
  cout << reverse(str, size);
}

I think you should take a minute to learn how to format posts using Markdown or HTML... — Tim Pietzcker
– Tim Pietzcker, Commented Mar 5, 2015 at 21:05
Can you clarify which space you are referring to? Might be best to give sample input and the corresponding sample output. Also, I would suggest that you surround the output with single quotes so you can actually tell where the string starts and ends. — Kevin Keane
– Kevin Keane, Commented Mar 5, 2015 at 21:05

vsoftco · Accepted Answer · 2015-05-19 13:28:09Z

2

Since you use std::string, you don't need to specify the size of the string, but use the std::string::size() or std::string::length() member functions. Also, a = str[size]; is problematic when size equals to the size of the string, since you perform an out of bound access (remember that C++ uses zero-based indexing). You can simplify the code a lot, ending up with

#include <iostream>
#include <cstddef> // for std::size_t

using namespace std;

string reverse(string str, std::size_t pos) {
    return (pos == 0 ? "" : str[pos - 1] + reverse(str, pos - 1));
}

int main() {
    string str;
    cout << "enter the word : ";
    getline(cin, str); // allow for spaces in the string
    cout << reverse(str, str.size()) << endl;
}

Here, instead of using cin >> str, I used getline(cin, str), since cin reads up to the first whitespace, whereas getline allows to read strings that containg spaces.

edited May 19, 2015 at 13:28

answered Mar 5, 2015 at 21:20

vsoftco

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Comments

Codor · Accepted Answer · 2015-03-05 21:06:17Z

1

Change the implementation of the function reverse to the following.

string reverse(string str ,int size){
    if (size==-1)
        return "";
    else
    {
        char a;
        a=str[size];
        if (' ' == a )
            return reverse(str,size-1)
        else
            return a+reverse(str,size-1);
    }
}

Alternatively, do some pre-processing on th input.

answered Mar 5, 2015 at 21:06

Codor

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2 Comments

Mohsin Mushtaq Over a year ago

e.g if i give input : "mohsin" output should be "nishom" and well that is fine it gives the same output but it includes the space before the output mohsin .............

Cole Tobin Over a year ago

@MohsinMushtaq Also, this is C++. The string class has a length value you can use without having to pass the size.

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