Palindromes with recursion

[kryptor]

Hi there,

Just need some help with this small program.

Using recursion I'm trying to find out if a word (in this case a test word) is a palindrome or not. If it is it should return a 1 to result, but instead it shows a big number that looks like a memory address.

Any guide will be deeply apreciated.



# include <stdio.h>
# include <process.h>
# include <string.h>

//Function prototype

int palindrome(char w[],int l,int r);


int
main (void)

{
int left=0;
int right=3;
int result=0;

char word[5]="deed"; //this is a test to check the function


result = palindrome (word,left,right);

printf("The word is %d\n",result ); //if the word is 1 its a palindrome
system("pause"); //if its 0 its not

return (0);
}


//palindrome function


int palindrome (char w [],int l, int r) //get parameters
{
if (r<=l) //base case 1 :we reached the end without problem
{
return (1);
}
else if (w [l] != w [r]) //base case 2 : the letters are not correct
{
return (0);
}
else
{
palindrome (w, (l+1),(r-1)); //recursive formula
}

}

[boxfish]

Hi,
The initial call to your recursive function does not return a value, so your result variable is uninitialized. Your palindrome function returns 1 if it's finished and the word is a palindrome, 0 if the word is discoverd not to be a palidrome, or it does not return anything. change

palindrome (w, (l+1),(r-1)); //recursive formula

to

return palindrome (w, (l+1),(r-1)); //recursive formula

Hope this helps.

[kryptor]

Thanks very much ! It worked perfectly !

[boxfish]

I'm glad it worked. However, it seems your code does not work when the palindrome has an odd number of letters.

[kryptor]

I'll check that , thanks again.