Recursive string reversal

This is a discussion on Recursive string reversal within the C++ Programming forums, part of the General Programming Boards category; I am trying to reverse a string using head() (first letter of a string) and tail() (all letters after the ...

  1. #1
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    Recursive string reversal

    I am trying to reverse a string using head() (first letter of a string) and tail() (all letters after the head) functions from a class I wrote. Everything is working alright except my output's not quite how I wanted it. For example, I input abcde, I should get edcba but this is what I get: edecdebcdea. as you can see it reverses it but still takes in all letters after the head (except for the original head):
    E De Cde Bcd de A. I'm new to recursion so I find this very confusing, any help would be appreciated. Thanks

    example output:
    Code:
    Enter a string:
    abcde
    x: abcde
    
    x: bcde
    
    x: cde
    
    x: de
    
    x: e
    
    x:
    
    mystring: edecdebcdea
    Here's the recursive function, I'm pretty sure the problem's somewhere in here:
    Code:
    strings reverse(strings x) 
        {
        cout<< "x: " <<x<<endl;                          //test output
        if (x.stringlength() <= 0)
    		{
    		return x;
    		}
    	return reverse(x.tail()) + x.head();        //recursive statement
        }
    relevant member functions from my class "strings"
    Code:
    /**********************************************************************
    	* Default Constructor:
    **********************************************************************/
    	strings::strings()					
    		{
    		int index = 0;
    		
    		while (index < 20)
    			{
    			strhead[index] = '\0';
    			strtail[index] = 't';
    			fullstring[index] = 'f';
    			index++;
    			}
    		head();
    		tail();
    		}
    		
    /**********************************************************************
    	* return string head
    **********************************************************************/
    	char *strings::head()
    		{
    		strncpy(strhead, fullstring, 1);
    		return strhead;
    		}
    	
    	/**********************************************************************
    	* Return string tail
    **********************************************************************/
    	strings strings::tail()
    		{
    		int index = 0;
    		strcpy(strtail, fullstring);
    		
    		//Test for null terminator
    		while (fullstring[index] != '\0')	
    			{
    			strtail[index] = fullstring[index + 1];
    			index++;
    			}
    		return strtail;
    		}
    	/**********************************************************************
    	*Return length of string 
    **********************************************************************/
    	int strings::stringlength()
    		{
    		return strlen(fullstring);
    		}
    	
    	/**********************************************************************
    	* Overloaded + operator
    	**********************************************************************/
    	strings strings::operator +(char right[1])
    		{
    		strcat(fullstring, right);
    		return fullstring;
    		}
    		
    /**********************************************************************
    	* Overloaded = operator
    	**********************************************************************/
    	void strings::operator =(const strings &right)
    		{
    		strcpy(fullstring, right.fullstring);
    		}

  2. #2
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    I tested your reverse algorithm and it works fine. It is therefore likely that it's the rest of your class methods that have problems. (Many of them look downright nonsensical.)
    System: Debian Sid and FreeBSD 7.0. Both with GCC 4.3.

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  3. #3
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    heres one that i have written before:
    Code:
    string reverse(string str, int loopNum=0)
    {
    	if (loopNum >= str.length())
    		return str;
    	str.insert(loopNum, str.substr(str.length()-1,1));
    	str = str.substr(0,str.length()-1);
    	return reverse(str,++loopNum);
    }
    to call the function pass one parameter, such as: cout << reverse("joe");

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Why not just use this?
    Code:
    void print_reverse(const char *str) {
        if(*str) {
            print_reverse(str+1);
            std::cout << *str;
        }
    }
    dwk

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