Palindrome Test

The palindrome test is very common in interviews. Here is a program that shows how to find out if a string is a palindrome.

Please note that this a simple program as in an interview not much more is expected from you. The test is not meant to commercialize your greatest palindrome rendition. We will not be buying palindrome testing software in the near future. The point of this test is to know your basic knowledge of string manipulation and algorithm generation. This program takes a string and tests whether the string is a palindrome or not. The palindrome can be one word long, or a whole sentence, and can have upper and lower case letters. Note that palindromes are not case sensitive. Also, the palindrome should ignore punctuation marks.

Please note that in my simple algorithm I am assuming that regular ASCII characters are used.

Algorithm:

1) Get string and lets call it testItem;
2) Strip all the punctuation marks, spaces, and symbols,
and store in testItemClean.
3) Reverse the testItem and store it into reverse.
4) Compare testItemClean and reverse.

To find more about palindromes please visit here .

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


int main()
{
   char testItem[] = "Was it Eliot's toilet, I saw?\0";
   int i = 0;
   int currentPointer = 0;
   int cPointerClean = 0;
   int length = (strlen(testItem))-1;
   char *reverse;
   char *testItemClean;

   reverse = (char*) malloc (length*sizeof(char));
   testItemClean = (char*) malloc (length*sizeof(char));
    
   for(i=0; i<=length; i++)
   {
      /*Reversing testItem and storing stripped 
       off symbols into *reverse*/
      
      if((testItem[length-i]>=65 && testItem[length-i]<=90) \
      ||((testItem[length-i]>=97 && testItem[length-i]<=122)))
      {
           if(testItem[length-i]>65 && testItem[length-i]<90)
                 testItem[length-i] = testItem[length-i] + 32; 
           reverse[currentPointer] = testItem[length-i];
           currentPointer++;
       } 

      /*Stripping testItem off symbols and storing into 
      testItemClean*/

      if((testItem[i]>=65 && testItem[i]<=90) \
      ||((testItem[i]>=97 && testItem[i]<=122)))
      {
           if(testItem[i]>65 && testItem[i]<90)
                 testItem[i] = testItem[i] + 32; 
           testItemClean[cPointerClean] = testItem[i];
           cPointerClean++;
      }

   }
   if(!strcmp(reverse, testItemClean))
           printf("It's a palindrome");
   getchar();
}