Find the largest palindrome made from the product of two 3-digit numbers

Question

package testing.project;

public class PalindromeThreeDigits {

    public static void main(String[] args) {
        int value = 0;
        for(int i = 100;i <=999;i+         


        

Answer 1

A slightly different approach that can easily calculate the largest palindromic number made from the product of up to two 6-digit numbers.

The first part is to create a generator of palindrome numbers. So there is no need to check if a number is palindromic, the second part is a simple loop.

#include 
#include 
#include 

using namespace std;
template 
class PalindromeGenerator {
    unique_ptr  m_data;
    bool m_hasnext;
public :
    PalindromeGenerator():m_data(new int[N])
    {
        for(auto i=0;i=0;i--){
        v+=m_data[i]*b;
        b*=10;
    }

    auto i=N-1;
    while (i>=0)
    {
        if(m_data[i]>=1) {
            m_data[i]--;
            return v;
        }
        else 
        {
            m_data[i]=9;
           i--; 
        }
    }

    m_hasnext=false;
    return v;
}


};

template
void findmaxPalindrome()
{
    PalindromeGenerator gen;
    decltype(gen.getnext()) minv=static_cast (pow(10,N-1));
    decltype(gen.getnext()) maxv=static_cast (pow(10,N)-1);
    decltype(gen.getnext()) start=11*(maxv/11);
    while(gen.hasNext())
    {
        auto v=gen.getnext();
        for (decltype(gen.getnext())  i=start;i>minv;i-=11)
        {
            if (v%i==0)
            {
                auto r=v/i;
                if (r>minv && r();
    return 0;
}