palindrome using pointers;

[vxk]

Q) Write a program that prints whther a given string is a palindrome or not.
write one function void checkPalindrome(char *str)

Can somebody guide with the following code

 
#include <iostream>
using namespace std;

void checkPalindrome(const char* p){
    
    const char* pnew = p;
    
    for(p;*p != '\0';p++);
  //  p--;
    while (*pnew++ == *--p);
    
    if(pnew>p) cout<<"is";

    else cout<<"isnot";
    
    
}
int main()
{
    int x;
    cout<<"enter the size of the string ";
    cin>>x;
    
    char* str = new char[x];
    
    for(int i = 0; i<x; i++){
        
        cin>>str[i] ;
    }
    
    const char* pointer;
    
    pointer = str;
    
    checkPalindrome(pointer);
    
    delete [] str;
   
    
    
}

The above code is only checking palindrome of 6 characters properly and
if i remove commenting on line 10 only 5 characters are checked .

[48T7M4Gy]

1. Why not just write cin>> str; instead of lines 27-30 inc?

2. Try also checkPalindrome( str ); at line 36?

:-)

[vxk]

after doing that even the 5 character word is not working….. can tell what is wrong with my checkPalindrome code ?

[48T7M4Gy]

Show us your code. I am runningyour code successfully on codeblocks for all sorts of lengths including 5.

PS with the couple of small changes I suggested. (Of course.)

PPS I didn't check your function logic because it worked. I'm lazy. But if it aint broken ...

[vxk]

Ohh yes its running fine ..!?!! thanks!

[vxk]

#include <iostream>
using namespace std;

void checkPalindrome(const char* p){
    
   const char* pnew = p;
  
    while(*++p);
  //  *p--;
    while (*pnew++ == *--p);

    if(pnew>p){
        cout<<"is";
    }
    else{
        cout<<"isnot";
    }
    
}
int main()
{
    int x;
cout<<"enter the size of the string ";
    cin>>x;
    
    char* str = new char[x];

   // for(int i = 0; i<x; i++){
        
        cin>>str ;
    //}
    
  // const char* pointer;
    
    checkPalindrome(str);
    
    delete [] str;
    
    
    
}

[vxk]

is there some way so that i can prevent the users from writing more than they entered .That is

if i entered size 2,
I will still be able to write more than 2 characters and the function is checking all of them !

for eg:

size entered : 2;
str entered : abcddcba;
output : is

how can i prevent this …

[48T7M4Gy]

One way is to accept a full line of text by getline() or whatever and then check that the length of that input complies before proceeding ...

[MiiNiPaa]

1) I suggest to read string in std::string and then call checkPalindrome(str.c_str())

2) Use const char* pnew = p + std::strlen(p); to make pnew pont to the end of the line.

3) while (*pnew++ == *p--); Has a danger of going out of bounds. Add sanity check for pointer:

while (*pnew++ == *p-- && p <= pnew)
    ;