Largest palindrome using string

004.palindromeLargest.cpp

// 004.palindromeLargest.cpp
// juanfc 2012-06-24
// A palindromic number reads the same both ways. The largest palindrome made
//  from the product of two 2-digit numbers is 9009 = 91 x 99.
// Find the largest palindrome made from the product of two 3-digit numbers.

#include <iostream>
#include <sstream>
using namespace std;

const int NOOFDIGITS = 3;

int largestPalWith(int N);
bool numIsPalind(int);
bool isPal(string s);

int main()
{

    cout << "The largest palindrome resulting of the mult. of numbers of "
         << NOOFDIGITS << " x " << NOOFDIGITS << " is: ";
    int greatestPal = largestPalWith(NOOFDIGITS);
    if ( greatestPal == 0 )
        cout << "None" << endl;
    else
          cout << greatestPal << endl;
    return 0;
}

int largestPalWith(int N)
{
    // find the limits
    int baseTop = 1;
    for (int i = 0; i < NOOFDIGITS; ++i) {
        baseTop *= 10;
    }
    int baseBot = baseTop / 10;

    int greatestPal = 0;
    int ii, jj;
    int test;
    for (int i = baseTop-1; i >= baseBot; i--) {
        for (int j = baseTop-1; j >= i; j--) {
            test = i * j;
            if (numIsPalind(test) and test > greatestPal) {
                greatestPal = test;
                ii = i;
                jj = j;
            }
        }
    }

    return greatestPal;
}

bool numIsPalind(int a)
{
    // here you need to convert the int to its decimal string chars
    // it can be done several ways:
    stringstream ss;
    ss << a;
    string s = ss.str();


    return isPal(s);
}

bool isPal(string s)
{
    int i = 0;
    int j = s.length()-1;

    while (i < j and s[i] == s[j]) {
        ++i;
        --j;
    }
    return i >= j;
}