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Jul 1st, 2008

help needed with C program using a linked list to determine if a word is a palindrome

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Hi,

i'm new to C programming and i could use some help with an assignment. i would like to store a word in a linked list, with each letter of the word in a separate node of the linked list. i would then like to traverse the linked list to check whether the word is a palindrome. the nodes in the palindrome should be double pointer nodes.

i'm not quite sure how to start here, any assistance will be appreciated.

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Jul 1st, 2008

Re: help needed with C program using a linked list to determine if a word is a palindrome

First you have to declare a structure that is each node. If you search for "linked lists" you will get lots of examples, such as this tutorial by Stanford University.

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Jul 1st, 2008

Re: help needed with C program using a linked list to determine if a word is a palindrome

i'll check the tutorial and see if that helps.

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Jul 2nd, 2008

Re: help needed with C program using a linked list to determine if a word is a palindrome

First create a doubly link list. A doubly link list with each nodes having the address of next and previous node. The structure of the such node is as follows:

c Syntax (Toggle Plain Text)
struct node {
        char data;
        node *next;
        node *prev;
};
struct node {
        char data;
        node *next;
        node *prev;
};

Then write some functions to add, delete and traverse etc And what write functions for what u exactly want.

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Jul 2nd, 2008

Re: help needed with C program using a linked list to determine if a word is a palindrome

thanks. each node is supposed to store one character of the entered word. the first and last letters of the word would then be compared and if the same, then the second would be compared to the second to last etc. what would be the best way to do this?

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Re: help needed with C program using a linked list to determine if a word is a palindrome

Ok!!

One thing more, you have to maintain two pointers..head and tail. Which will have the addresses of first and last node respectively.

And write a function which will count the length of the link list (ie number of characters).

Once that is done you can loop through the list in this way:

c Syntax (Toggle Plain Text)
//Assuming that head and tail are global
int isPalindrome() {
       node *tempHead = head;
       node *tempTail = tail;
 
       //function to calculate the length of link list
       int length = getLength();
       int i = 0;
       for(;i<length/2;i++) {
             if(tempHead->data != tempTail->data)
                  return 0;
 
             tempHead = tempHead->next;
             tempTail = tempTail->prev;
      }
      return 1;
}
//Assuming that head and tail are global
int isPalindrome() {
       node *tempHead = head;
       node *tempTail = tail;
     
       //function to calculate the length of link list
       int length = getLength();
       int i = 0;
       for(;i<length/2;i++) {
             if(tempHead->data != tempTail->data)
                  return 0;
       
             tempHead = tempHead->next;
             tempTail = tempTail->prev;
      }
      return 1;
}

Hope u got it.

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Re: help needed with C program using a linked list to determine if a word is a palind

Last edited by Adak; Jul 2nd, 2008 at 3:58 am.

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Jul 3rd, 2008

Re: help needed with C program using a linked list to determine if a word is a palindrome

Thanks a whole lot man!

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