Need help reversing an entered String with recursion

skis0601 · #1 03-Dec-2007, 03:17

Hi there I am trying to write a short program to read in an entered string and then reverse it using recursion. my program is reading it ok but as far as I can tell its not stopping at the end of the string so it never prints the reversed string. Can any1 help out?

CPP / C++ / C Code:

void fib(char &);

int main()
{
  char ch;

  cout << "Enter a String: ";
  fib(ch);

  return EXIT_SUCCESS;
}

void fib(char &ch)
{
  cin.get(ch);
  fib(ch);
  cout << ch;
}

ahbi82 · #2 03-Dec-2007, 03:29

Quote:

Originally Posted by skis0601

Hi there I am trying to write a short program to read in an entered string and then reverse it using recursion. my program is reading it ok but as far as I can tell its not stopping at the end of the string so it never prints the reversed string. Can any1 help out?

CPP / C++ / C Code:

void fib(char &);

int main()
{
  char ch;

  cout << "Enter a String: ";
  fib(ch);

  return EXIT_SUCCESS;
}

void fib(char &ch)
{
  cin.get(ch);
  fib(ch);
  cout << ch;
}

From my point of view, i don't this recursion is necessary. By running a for loop with a swap function is sufficient.

CPP / C++ / C Code:

void swapChar( char* a, char* p )
{
    char temp;

    temp = *a;
    *a = *b;
    *b = temp;
}

The for loop will run half for the string length times and calling the swapChar function. Take note, that swap from the start and the end of the string.

Hope this helps!!

}

skis0601 · #3 03-Dec-2007, 03:40

unfortunately the purpose of this program is to test recursion so I do need to use it.

Kimmo · #4 03-Dec-2007, 06:38

Just look at what your program is doing.

CPP / C++ / C Code:

void fib(char &ch)
{
  cin.get(ch);        // let's get some input
  fib(ch);              // let's call fib() to get some input and to call fib() to get some input and to call fib() to get some input and to call fib() to get some...
  cout << ch;
}

In other words, there's nothing to break the recursion.

I would do it with something as follows..

CPP / C++ / C Code:

#include <iostream>
#include <string>

using namespace std;

void reverseString(string& String, int position);

int main()
{
  string String;

  cout << "Enter a String: ";
  getline(cin, String);

  reverseString(String, String.size() - 1);

  return EXIT_SUCCESS;
}

void reverseString(string& String, int position)
{
    cout << String[position];
    if (position > 0)
    {
        reverseString(String, position -1 );
    }
}

inevitable · #5 03-Dec-2007, 07:58

Take the below example it will work....

CPP / C++ / C Code:

#include <stdio.h>
 
void revString(char *s, int pos);
 
void main()
{
        char str[100];
        char ch;
        int i=0;
        printf("Enter any string: ");
        do
        {
            scanf("%c",&ch);
            str[i] = ch;
            i++;
        }while(ch!=10);
        str[i]='\0';
        printf("\nOriginal String is %s",str);
        printf("\nString after recursion is : ");
        revString(str,i);
}
 
void revString(char *str,int pos)
{
    if(pos<0)
    {
        return;
    }
    else
    {
        printf("%c",str[pos]);
        revString(str,pos-1);
    }
}

Peter_APIIT · #6 03-Dec-2007, 18:41

Kimmo has produced a good program here.

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Need help reversing an entered String with recursion

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