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#pragma once
#include <iostream>
#include <optional>
#include <string_view>
#include <cstdint>
using namespace std;
const int N = 9;
const int BOARDMID = N * (N/2) + N/2;
const uint8_t EMPTY = 0, WHITE = 1, KING = 2, BLACK = 4;
struct Move {
int from, to;
Move() = default;
Move(int from, int to);
static optional<Move> parse(string_view str);
};
struct Board {
uint8_t cells[N * N];
static Board makeInitial();
void apply(Move mv);
int applyCW(Move mv);
int checkWin() const; // 1=win white, -1=win black, 0=none yet
bool isValid(Move mv, int player) const;
// Calls the callback for each valid move of the specified player.
// F should have a signature compatible with bool F(Move mv).
// If the callback returns true, iteration is stopped.
// Callback should not modify this Board instance.
template <typename F>
void forEachMove(int player, F callback) const;
private:
Board();
bool isValid(Move mv) const;
bool stoneFlankedH(int pos, uint8_t by) const;
bool stoneFlankedV(int pos, uint8_t by) const;
bool kingEncircled(int pos) const;
};
ostream& operator<<(ostream &os, const Move &mv);
ostream& operator<<(ostream &os, const Board &bd);
template <typename F>
void Board::forEachMove(int player, F callback) const {
static const int deltas[4][2] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};
for (int y = 0; y < N; y++)
for (int x = 0; x < N; x++) {
uint8_t v = cells[N * y + x];
if (player == 1 ? v != WHITE && v != KING : v != BLACK) continue;
for (int i = 0; i < 4; i++) {
int x2 = x + deltas[i][0], y2 = y + deltas[i][1];
while (x2 >= 0 && x2 < N && y2 >= 0 && y2 < N) {
if (cells[N * y2 + x2] != EMPTY) break;
if (N * y2 + x2 != BOARDMID) {
callback(Move(N * y + x, N * y2 + x2));
}
x2 += deltas[i][0];
y2 += deltas[i][1];
}
}
}
}
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