Palidromes

how do you write a program about a palidrome withoust using the STL.

That is create a program that takes a string of character like "civic or rotator" and check if it is a palidrome without using the standard template library.

thanks

I would start by doing something like:

Getting the size of the string.
Looping through with two counters, one set to 0, the other at the size of the string -1 (?), and comparing each letter of the string to see if they match, until i get to the middle letter (if there is one)

Code:

---


#include <string>

char String[50];
int C1 = 0;
int C2 = 0;

int main()
    {
    // Get the string
    C2 = strlen(String);


   
    while (C1 != (strlen(String) / 2))
          {
          if (String[C1] != String[C2])
              cout << "Not a pallendrome!";
          else
              C1++; C2--;
          }
    }

---

Theres other ways you might compare though, such as comparing the letters in the loop and setting flags or something, but thats up to you.

Code:

---

#include < iostream >
#include < cstring >

bool isPalindrome( char *start )
{
    // point at the last element
    char *end = start + std::strlen ( start ) - 1;

    // case insensitive comparison
    std::strlwr ( start );

    do{
        if ( *start != *end )
            return false;
    }while ( ++start < --end );

    return true;
}

int main()
{
    char candidate[] = "Civic or rotator";

    std::cout << candidate;

    if ( isPalindrome( candidate ) )
        std::cout << " is a palindrome.\n";
    else
        std::cout << " is not a candidate.\n";

    return 0;
}

---

edit: typo.

Quote:

---

Originally posted by stovellp

Code:

---


#include <string>

char String[50];
int C1 = 0;
int C2 = 0;

int main()
    {
    // Get the string
    C2 = strlen(String);


   
    while (C1 != (strlen(String) / 2))
          {
          if (String[C1] != String[C2])
              cout << "Not a pallendrome!";
          else
              C1++; C2--;
          }
    }

---

---

This will trap you in an infinite loop printing "Not a pallendrome!" because String[C2] the first time through will point at the terminating null, causing control to enter the body of the if statement. Since else will be skipped, this will continue, and continue....

edit: There's more problems here. the C2 decrement is not part of the else statement (no brackets) and <string> is included, but no std namespace is used. BTW string is the STL string container, cstring or string.h is the C-style string header.

-Futura

Yeah your right, if I had compiled and tested this I would have fixed those errors. Its amazing what silly mistakes i make when I dont actually test my code :).

It is also amazing that people will do other peoples homework for them, and that questioners asking one of the commonest basic homework assignments out do not search the board for the dozens of other times this has been asked here.

Yeah but hey, I asked thousands of basic questions back in my younger days here (about a year ago), although they weren't for homework. So I thought I ought to give something back, since I did (almost, close enough) know the answer to this.

All I would have done differently was to have the counters Increment and decrement in the loop not in the IF statement and start C2 at one less than it was. I didn't expect my code would be used, and so didn't put much into doing it, it was meant to serve as an example of what could be done.

> It is also amazing that people will do other peoples homework for them


You're absolutely right adrianxw, my bad. No more free answers from me! Although I will say that for me personally, I have learned as much by scrutinizing well-written code as by figuring something out by myself. There's a place for both. I suppose it also has to do with your desire and integrity as a learner. :)

>>> I suppose it also has to do with your desire and integrity as a learner.

That is so true.

Hey for you information this is not an homework. This is just something i tried doing on my own.
See the palidrome you guys are doing i know that, but what i was asking was

could you test for a palidrome wiothout using the STL's we have like
#include<string>

>>>
and that questioners asking one of the commonest basic homework assignments out do not search the board for the dozens of other times this has been asked here.
<<<

Closed.