Question

In C++, create a recursive bool function which determines if a string is symmetrical or not. A symmetrical string can be read the same front to back (ex. kayak).

Function Blueprint

---------------------

bool isSymmetrical(string s)

if (s is the empty string or s is of length 1)

return true

else if (s's first and last characters are the same letter)

  return isSymmetrical (s minus its first and last characters)

else
return false

Answer 1

recursive function

bool isSymmetrical(char string[])
{
   int n;
   for(n=0;string[n]!='\0';n++);//find the length of the string
     
   static int lowerIndex=0,upperIndex=n-1;
//condition for the string having single character
if (lowerIndex == upperIndex)
{
return true;
}
//if any mismatch found then return false
//first character and last character will compare
if (string[lowerIndex] != string[upperIndex])
{
return false; //return false
}
//if no mismatch is found then recursively call to the method
if (lowerIndex < upperIndex+1)
{
   lowerIndex= lowerIndex+1; //increase the value of lowerIndex
   upperIndex = upperIndex-1; //decrease the value of upperIndex
return isSymmetrical(string); //call recursively()
}
//if all the characters match then return true
return true;
}

PROGRAMMING IMPLEMENTATION

#include <iostream>

using namespace std;
bool isSymmetrical(char string[])
{
   int n;
   for(n=0;string[n]!='\0';n++);//find the length of the string
     
   static int lowerIndex=0,upperIndex=n-1;
//condition for the string having single character
if (lowerIndex == upperIndex)
{
return true;
}
//if any mismatch found then return false
//first character and last character will compare
if (string[lowerIndex] != string[upperIndex])
{
return false; //return false
}
//if no mismatch is found then recursively call to the method
if (lowerIndex < upperIndex+1)
{
   lowerIndex= lowerIndex+1; //increase the value of lowerIndex
   upperIndex = upperIndex-1; //decrease the value of upperIndex
return isSymmetrical(string); //call recursively()
}
//if all the characters match then return true
return true;
}

// Driver Program
int main()
{
char string[100];
   cout<<endl<<"Enter the string";
   gets(string);//read the string
if ( isSymmetrical(string)) //condition for symmetric string
cout<<string<<" is symmetric"<<endl;
else
cout<<string<<" is not symmetric"<<endl;
return 0;
}

output