Why the function is not returning the string?

Question

#include<iostream>
#include<string.h>
using namespace std;

string revString(string s,string copy,int i,int j)
{   
    if(i==s.length())
        return copy;//if 'i' reaches to the length of the string it returns the copied value
    else{
        copy[i]=s[j];//copying the string s into copy
        return revString(s,copy,++i,--j);// calling recursively 
    }
}

int main()
{
    string s,copy;
    cout<<"Enter a string without entering spaces\n";   
    cin>>s;
    int i=0,j=s.length()-1;
    cout<<revString(s,copy,i,j);//function for reversing the string
    return 0;
}

here i am trying to copy the string 's' into the string 'copy' by using recursion but the function isn't returning anything.

Answer 1

Because you have not allocated memory to your copy variable, but trying to assign values to it. I would suggest you to read more about memory allocation in C++ string class.

With minimum alterations to your code, you can make it work by adding the following snippet just before calling your revString() function:

copy.resize(s.size());