Tic Tac Toe Board Encoding and Comparing (TTTBEC for short)

encoding.cpp

#include <iostream>
#include <vector>
#include <array>

using namespace std;

template<typename T>
using board = vector<vector<T> >;

typedef array<char, 3> encoding;

const char X = 1; // cross
const char O = 3; // circle
const char U = 0; // Undefined / empty

encoding encode(const board<int> &b) {
    encoding rv;
    // encode center
    rv[0] = b[1][1];

    // encode corners
    rv[1] = (b[0][0]) | (b[0][2] << 2) | (b[2][0] << 6) | (b[2][2] << 4);

    // encode cross
    rv[2] = (b[0][1]) | (b[1][0] << 6) | (b[1][2] << 2) | (b[2][1] << 4);

    return rv;
}

constexpr char rol(char c, unsigned n) {
    return (c << n) | (c >> (8 - n));
}

bool match(const encoding& a, const encoding& b) {
    if(a[0] != b[0])
        return false;
    if(a[1] == b[1])
        return a[2] == b[2];
    if(a[1] < b[1])
        return match(b, a);
    int i = 0;
    while(i < 6)
        if(rol(a[1], i) == b[1])
            return rol(a[2], i) == b[2];
        else
            i += 2;
    return false; 
}

void print_bits(const char& c) {
    for(int i = 7; i >= 0; i--) {
        if((1 << i) & c)
            cout << "1";
        else
            cout << "0";
        if(i%2==0)
            cout << " ";
    }
    cout << endl;
}

void print_encoding(const encoding& e) {
    print_bits(e[0]);
    print_bits(e[1]);
    print_bits(e[2]);
}

int main() {
    board<int> a = {{X,U,U},
                    {O,O,U},
                    {U,U,U}};
    board<int> b = {{U,U,U},
                    {U,O,U},
                    {X,O,U}};
    encoding e1 = encode(a);
    encoding e2 = encode(b);
    print_encoding(e1);
    cout << endl;
    print_encoding(e2);
    cout << endl << boolalpha << match(e1, e2) << endl;
    return 0;
}