给出C语言详细的六子棋AI博弈树代码并逐行注释

对于六子棋AI博弈树的代码，下面是一个简单的示例程序。由于代码较长，我在注释中进行了详细的解释，希望对你有所帮助。

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

// 定义棋盘大小为 6 * 6
#define BOARD_SIZE 6

// 定义棋子类型
typedef enum { EMPTY, BLACK, WHITE } piece_t;

// 定义博弈树节点类型
typedef struct node {
    // 当前棋盘状态
    piece_t board[BOARD_SIZE][BOARD_SIZE];
    // 当前节点的下一步落子颜色，BLACK 代表黑方，WHITE 代表白方
    piece_t next_piece;
    // 当前节点的估值，用于评估当前节点的价值
    int value;
    // 当前节点的子节点数组
    struct node *children[BOARD_SIZE * BOARD_SIZE];
    // 子节点数量
    int num_children;
} node_t;

// 初始化棋盘
void init_board(piece_t board[BOARD_SIZE][BOARD_SIZE]) {
    for (int i = 0; i < BOARD_SIZE; i++) {
        for (int j = 0; j < BOARD_SIZE; j++) {
            board[i][j] = EMPTY;
        }
    }
}

// 打印棋盘
void print_board(piece_t board[BOARD_SIZE][BOARD_SIZE]) {
    printf("  ");
    for (int i = 0; i < BOARD_SIZE; i++) {
        printf("%d ", i);
    }
    printf("\n");
    for (int i = 0; i < BOARD_SIZE; i++) {
        printf("%d ", i);
        for (int j = 0; j < BOARD_SIZE; j++) {
            if (board[i][j] == EMPTY) {
                printf("- ");
            } else if (board[i][j] == BLACK) {
                printf("X ");
            } else {
                printf("O ");
            }
        }
        printf("\n");
    }
}

// 判断某一方是否胜利
int is_win(piece_t board[BOARD_SIZE][BOARD_SIZE], piece_t piece) {
    // 判断横向
    for (int i = 0; i < BOARD_SIZE; i++) {
        for (int j = 0; j <= BOARD_SIZE - 6; j++) {
            int count = 0;
            for (int k = 0; k < 6; k++) {
                if (board[i][j + k] == piece) {
                    count++;
                }
            }
            if (count == 6) {
                return 1;
            }
        }
    }
    // 判断纵向
    for (int i = 0; i <= BOARD_SIZE - 6; i++) {
        for (int j = 0; j < BOARD_SIZE; j++) {
            int count = 0;
            for (int k = 0; k < 6; k++) {
                if (board[i + k][j] == piece) {
                    count++;
                }
            }
            if (count == 6) {
                return 1;
            }
        }
    }
    // 判断正斜线
    for (int i = 0; i <= BOARD_SIZE - 6; i++) {
        for (int j = 0; j <= BOARD_SIZE - 6; j++) {
            int count = 0;
            for (int k = 0; k < 6; k++) {
                if (board[i + k][j + k] == piece) {
                    count++;
                }
            }
            if (count == 6) {
                return 1;
            }
        }
    }
    // 判断反斜线
    for (int i = 0; i <= BOARD_SIZE - 6; i++) {
        for (int j = 5; j < BOARD_SIZE; j++) {
            int count = 0;
            for (int k = 0; k < 6; k++) {
                if (board[i + k][j - k] == piece) {
                    count++;
                }
            }
            if (count == 6) {
                return 1;
            }
        }
    }
    return 0;
}

// 评估当前节点的价值
int evaluate(node_t *node) {
    // 如果当前节点是黑方胜利，则其价值为正无穷大
    if (is_win(node->board, BLACK)) {
        return INT_MAX;
    }
    // 如果当前节点是白方胜利，则其价值为负无穷大
    if (is_win(node->board, WHITE)) {
        return INT_MIN;
    }
    // 否则，计算黑方棋子数和白方棋子数的差值
    int black_count = 0, white_count = 0;
    for (int i = 0; i < BOARD_SIZE; i++) {
        for (int j = 0; j < BOARD_SIZE; j++) {
            if (node->board[i][j] == BLACK) {
                black_count++;
            } else if (node->board[i][j] == WHITE) {
                white_count++;
            }
        }
    }
    return black_count - white_count;
}

// 创建新节点
node_t *new_node(piece_t board[BOARD_SIZE][BOARD_SIZE], piece_t next_piece) {
    node_t *node = (node_t *)malloc(sizeof(node_t));
    for (int i = 0; i < BOARD_SIZE; i++) {
        for (int j = 0; j < BOARD_SIZE; j++) {
            node->board[i][j] = board[i][j];
        }
    }
    node->next_piece = next_piece;
    node->value = evaluate(node);
    node->num_children = 0;
    return node;
}

// 销毁节点
void destroy_node(node_t *node) {
    for (int i = 0; i < node->num_children; i++) {
        destroy_node(node->children[i]);
    }
    free(node);
}

// 获取当前节点的所有子节点
void get_children(node_t *node) {
    for (int i = 0; i < BOARD_SIZE; i++) {
        for (int j = 0; j < BOARD_SIZE; j++) {
            if (node->board[i][j] == EMPTY) {
                node->children[node->num_children] = new_node(node->board, node->next_piece == BLACK ? WHITE : BLACK);
                node->children[node->num_children]->board[i][j] = node->next_piece;
                node->children[node->num_children]->value = evaluate(node->children[node->num_children]);
                node->num_children++;
            }
        }
    }
}

// 极大极小搜索算法
int minimax(node_t *node, int depth, int alpha, int beta, int maximizing_player) {
    // 如果当前节点已经是叶子节点，返回其估值
    if (depth == 0 || node->num_children == 0) {
        return node->value;
    }
    // 如果当前节点是极大节点
    if (maximizing_player) {
        int max_value = INT_MIN;
        for (int i = 0; i < node->num_children; i++) {
            int value = minimax(node->children[i], depth - 1, alpha, beta, 0);
            max_value = value > max_value ? value : max_value;
            alpha = alpha > max_value ? alpha : max_value;
            if (beta <= alpha) {
                break;
            }
        }
        return max_value;
    } else {
        int min_value = INT_MAX;
        for (int i = 0; i < node->num_children; i++) {
            int value = minimax(node->children[i], depth - 1, alpha, beta, 1);
            min_value = value < min_value ? value : min_value;
            beta = beta < min_value ? beta : min_value;
            if (beta <= alpha) {
                break;
            }
        }
        return min_value;
    }
}

// 获取 Alpha-Beta 剪枝后的最佳下法
void get_best_move(piece_t board[BOARD_SIZE][BOARD_SIZE], piece_t next_piece, int depth, int *x, int *y) {
    // 创建根节点
    node_t *root = new_node(board, next_piece);
    // 获取根节点的所有子节点
    get_children(root);
    // 初始化最佳下法的值
    int best_value = INT_MIN;
    // 遍历根节点的所有子节点，找到 Alpha-Beta 剪枝后的最佳下法
    for (int i = 0; i < root->num_children; i++) {
        int value = minimax(root->children[i], depth - 1, INT_MIN, INT_MAX, 0);
        if (value > best_value) {
            best_value = value;
            *x = i / BOARD_SIZE;
            *y = i % BOARD_SIZE;
        }
    }
    // 销毁根节点及其所有子节点
    destroy_node(root);
}

int main() {
    // 初始化棋盘
    piece_t board[BOARD_SIZE][BOARD_SIZE];
    init_board(board);
    // 黑方先手
    piece_t next_piece = BLACK;
    // 打印棋盘
    print_board(board);
    // 开始循环下棋
    while (1) {
        // 如果当前是黑方下棋
        if (next_piece == BLACK) {
            int x, y;
            // 获取 Alpha-Beta 剪枝后的最佳下法
            get_best_move(board, next_piece, 3, &x, &y);
            // 在棋盘上落子
            board[x][y] = next_piece;
            // 打印棋盘
            print_board(board);
            // 判断是否胜利
            if (is_win(board, next_piece)) {
                printf("BLACK win!\n");
                break;
            }
            // 切换到白方下棋
            next_piece = WHITE;
        } else {
            // 如果当前是白方下棋
            int x, y;
            // 获取 Alpha-Beta 剪枝后的最佳下法
            get_best_move(board, next_piece, 3, &x, &y);
            // 在棋盘上落子
            board[x][y] = next_piece;
            // 打印棋盘
            print_board(board);
            // 判断是否胜利
            if (is_win(board, next_piece)) {
                printf("WHITE win!\n");
                break;
            }
            // 切换到黑方下棋
            next_piece = BLACK;
        }
    }
    return 0;
}

注：该示例程序实现了一个简单的六子棋AI博弈树，但并不是最优解，你可以根据实际需要进行修改和优化。