amoba.cc

#include <vector>
#include <array>
#include <cstdio>
#include <iostream>
#include <random>


enum State: unsigned char {
	Empty,
	X,
	O
};

#define TABLE_SIZE 3

typedef std::array<std::array<State, TABLE_SIZE>, TABLE_SIZE> Table;

static bool wins(const Table &table, State player)
{
	// three in a row?
	for (auto &row : table) {
		if (row == std::array<State, TABLE_SIZE> {{ player, player, player }}) {
			return true;
		}
	}

	// Three in a column?
	for (int i = 0; i < TABLE_SIZE; i++) {
		if (table[0][i] == player && table[1][i] == player && table[2][i] == player) {
			return true;
		}
	}

	// Three in a diagonal?
	return table[0][0] == player && table[1][1] == player && table[2][2] == player
	    || table[0][2] == player && table[1][1] == player && table[2][0] == player;
}

static void print_table(const Table &table) {
	const char chars[] = { ' ', 'X', 'O' };

	for (auto &row : table) {
		for (auto cell : row) {
			std::printf("  %c  |", chars[cell]);
		}
		std::printf("\n-----+-----+-----+\n");
	}

	std::printf("\n");
}

struct Coord {
	int r, c;
};

Coord get_input() {
	Coord coord;
	std::cin >> coord.r >> coord.c;
	return coord;
}

bool place_ai(Table &table) {

	for (auto &row : table) {
		for (auto &cell : row) {
			if (cell != Empty) {
				continue;
			}

			auto tmp_cell = cell;
			cell = X;

			if (wins(table, X)) {
				return true;
			} else if (place_ai(table)) {
				cell = tmp_cell;
				return true;
			}

			cell = tmp_cell;
		}
	}

	return false;
}

int main()
{
	Table table
	{{
			{{ Empty, Empty, Empty }},
			{{ Empty, Empty, Empty }},
			{{ Empty, Empty, Empty }},
	}};

	std::uniform_int_distribution<int> dist(0, 2);
	std::random_device rd;

	int r = dist(rd), c = dist(rd);
	table[r][c] = X;

	while (!wins(table, X) && !wins(table, O)) {
		print_table(table);

		while (true) {
			auto player_coord = get_input();
			if (table[player_coord.r][player_coord.c] == Empty) {
				table[player_coord.r][player_coord.c] = O;
				break;
			} else {
				printf("You can't place an 'O' there. Retry.\n");
			}
		}

		place_ai(table);
	}

	print_table(table);
	std::printf("'%c' wins!\n", wins(table, X) ? 'X' : 'O');
	return 0;
}