Palindrome emordnilaP

Program compiles fine. Does not make the correct decisions for palindrome determination. Show me the path to coding goodness;



Entire code here.


Suspect code here:

Code:

while(flag && ptr)
             {
                 if(!strcmp(&temp[index], &ptr->letter))
                      
                     flag=false;
                 
                 ptr=ptr->next;
                 index++;
             }

If oyu compare it letter by letter you don't need to use strcmp. Just compare the border letters then recursiverly (semantically speaking) check substring NOT containing these letters. This can be implemented using a simple loop:

Code:

bool IsPalindrome(const std::string& String)
{
  int First = 0;
  int Last = static_cast<int>(String.size()) - 1;

  while(First < Last)
  {
    if(String[First] != String[Last]) return false;
    
    First++;
    Last--;
  }

  return true;
}

Code:

int IsPalindrome( char* word, int length)
{
   if( length <= 1) return 1;
   else
   return ( (word[0] == word[length-1]) && IsPalindrome(word+1,length-2));
}

Which naturally fails if you're testing anything other than a single word like "wow" "mom" "dad", etc. If you have any spaces, your test fails, unless it's perfectly aligned.

Quzah.

mine?
seems to work excellently. here try for yourself. cant get it to fail.

Code:

#include <iostream>
#include <string>

int IsPalindrome( const char* word, size_t length)
{
   if( length <= 1) return 1;
   else
   return ( (word[0] == word[length-1]) && IsPalindrome(word+1,length-2));
}

int main()
{
   std::string test;
   std::cout<<" enter string.... ";
   std::getline(std::cin,test);
   if (IsPalindrome(test.c_str(),test.length()))
      std::cout<<std::endl<<"palindrome"<<std::endl;
   else
      std::cout<<std::endl<<" not palindrome"<<std::endl;
   getchar();
}

I think he refers to a string like:

"ab cba"

which would fail...

but thats not a palindrome obviously
anyway it would be simple matter to strip spaces before testing.
mom dad wow dad mom
thats a palindrome
momdad wow dad mom
is not a palindrome. Sure the letters appear in same order but it is not a palindrome it doesnt read same backwars as forwards.

well is "ab cba" a palindrome? I don't think so

nor i

I was under the impression that spaces didn't count. I mean how many palindromes are left otherwise?

Also, palindrome sites exclude spaces.
ex: http://www.palindromelist.com/

well at the top of the page they have this....

Palindrome: A word, phrase, verse, or sentence that reads the same backward or forward.

and yet they try to tell you that this is a palindrome...

A dog! A panic in a pagoda!

which backwards is obviously....

!adogap a ni cinap a !god A

really doesnt read same backwards as forwards, but hell if that really what you want as i said previously its incredibly simple to strip spaces and punctuation.

Most of these homework palindrome posts don't care about spaces. It's quite common, as anyone who has been around here for any time can tell you. Which is why I made the comment.

While it may be trivial to ignore whitespace, yours didn't, which again is why I made the comment. So to recap:

common palindrome problem + code that doesn't account for it = my reply telling you it doesn't fulfill the common palindrome problem

Do a forum search for palindrome if you're still in doubt.

Quzah.

well you learn something everyday. I really thought a palindrome was of the straw warts variety. And I agree my code will not as it is find palindromes with spaces/punctuation in unless they are true mirror images but even so stripping that punctuation and spaces from the string it will do an admirable job. As its homework left as an exercise for the OP.

Bored again doh!

Code:

#include <iostream>
#include <string>
#include <cctype>

int IsMirrorPalindrome( const char* word, size_t length )
{
   if( length <= 1) return 1;
   else
   return ( (word[0] == word[length-1]) && IsMirrorPalindrome(word+1,length-2));
}

int IsPalindrome(std::string test)
{
   std::string tempcopy;
   std::string::iterator iter = test.begin();
   const std::string::iterator end = test.end();
   while ( iter != end )
   {
      const char c = *iter;
      if ( (!std::ispunct(c)) && (!std::isspace(c)) ) tempcopy.push_back(std::tolower(c));
      ++iter;
   }

   if (IsMirrorPalindrome(tempcopy.c_str(),tempcopy.length()))
      return 1;
   else
      return 0;
}


int main()
{
   std::string test;
   std::cout<<" enter string.... ";
   std::getline(std::cin,test);
   if (IsPalindrome(test))
      std::cout<<std::endl<<"palindrome"<<std::endl;
   else
      std::cout<<std::endl<<" not palindrome"<<std::endl;
   getchar();
}

me too!

Code:

bool isPalindrome(const char * data) 
{
 for(const char * tail = data + strlen(data) - 1; data < tail; tail--, data++) 
 {
  while(isspace(*data) || ispunct(*data)) data++;
  while(isspace(*tail) || ispunct(*tail)) tail--; 
  if(data < tail) 
  {
   if(*data != *tail) return false;
  }  
 }
 return true;  
}