A question I've been asked on interactive phone screens is to code a test to determine whether a string is a palindrome or not. I provide two examples here, one in C and one in C++. They both work and they both compile without errors or warnings. I believe my C example is good, with the possible exception of variable names (some of you may not like the register char* declarations, but the are valid in 'C').

My goal was an O(N) solution with out reversing the string.

My question is about the C++ version, and I miss using iterators? Is there a way to make this more C++ like?

I can think in C, I can't necessarily thing in C++.

Palindrome checker in C

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

bool palindromeChecker(char *possiblePalindrome)
{
    bool isPalindrome = true;
    size_t length = strlen(possiblePalindrome);
    
    if (length < 3)
    {
        isPalindrome = false;
    }
    else
    {
        register char *leftSide = possiblePalindrome;
        register char *rightSide = &possiblePalindrome[length-1];
        
        while ((leftSide < rightSide) && isPalindrome)
        {
            if (*leftSide != *rightSide)
            {
                isPalindrome = false;
            }
            leftSide++;
            --rightSide;
        }
    }
    
    return isPalindrome;
}

int main(int argc, const char * argv[]) {
    char testString[BUFSIZ];
    bool iSPalendrome;
    
    printf("Enter a test string to be checked for if it is a palindrome\n");
    scanf("%s", testString);
    iSPalendrome = palindromeChecker(testString);
    printf("The test string %s is %s a palindrome\n", testString, (iSPalendrome? "" : "Not"));
    
}

Palindrome checker in C++

#include <iostream>
#include <string>

bool IsPalindrome(std::string PossiblePalindrome)
{
    bool Palidrime = true;
    
    if (PossiblePalindrome.size() < 3)
    {
        Palidrime = false;
    }
    else
    {
        std::string::iterator leftSide = PossiblePalindrome.begin();
        std::string::iterator rightSide = PossiblePalindrome.end();
        rightSide--; // end is past the end of the possible palindrome so decrement to point to a character.
        
        while ((leftSide < rightSide) && Palidrime)
        {
            if (*leftSide != *rightSide)
            {
                Palidrime = false;
            }
            leftSide++;
            rightSide--;
        }
    }
    
    return Palidrime;
}

int main(int argc, const char * argv[]) {
    // insert code here...
    std::string PossiblePalindrome;
    std::cout << "Enter a string to test to see if it is a palindrome.\n";
    std::cin >> PossiblePalindrome;
    
    std::cout << "The string " << PossiblePalindrome;
    if (IsPalindrome(PossiblePalindrome))
    {
        std::cout << " is";
    }
    else
    {
        std::cout << " is not";
    }
    std::cout << " a palindrome" << std::endl;
}