井字棋小游戲（C語言）

最近沉迷於《NetHack》、《DCSS》等字符界面游戲，對其很感興趣，於是用C語言寫了個字符界面的井字棋小游戲，作為練手。代碼寫得不好。歡迎大家指教。

編寫時遇到了一些問題，我原先准備用循環，直到讀取到正確的輸入。可該死的getchar函數，在讀取后，又把回車又傳給下次循環，我不得不對其進行處理。

設定井字棋的AI時，有個有趣的地方就是，先下四個角比先下中心優勢更大，這違背了我以前的直覺。

#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>

void drawBoard(char *board) //繪制棋盤
{
    printf("%c|%c|%c\n", board[7], board[8], board[9]);
    puts("-+-+-");
    printf("%c|%c|%c\n", board[4], board[5], board[6]);
    puts("-+-+-");
    printf("%c|%c|%c\n", board[1], board[2], board[3]);
    puts("-+-+-");
}

char inputPlayerLetter() //玩家選擇棋子
{
    char letter;
    puts("你想用X還是O?");
    do{
        letter = toupper(getchar());
        if (letter == '\n')
            continue;
        if (letter != 'X' && letter != 'O')
            puts("你想用X還是O?");
    }while (letter != 'X' && letter != 'O');
    
    return letter;

}

void makeMove(char *board,char letter,int move) //落子
{
    board[move] = letter;
}

_Bool isWinner(char *bo, char le) //判定是否獲勝
{
    return ((bo[7] == le && bo[8] == le && bo[9] == le) ||
        (bo[4] == le && bo[5] == le && bo[6] == le) ||
        (bo[1] == le && bo[2] == le && bo[3] == le) ||
        (bo[7] == le && bo[4] == le && bo[1] == le) ||
        (bo[8] == le && bo[5] == le && bo[2] == le) ||
        (bo[9] == le && bo[6] == le && bo[3] == le) ||
        (bo[7] == le && bo[5] == le && bo[3] == le) ||
        (bo[9] == le && bo[5] == le && bo[1] == le));
}

const char getBoardCopy(char *board) //復制棋盤，讓電腦預判可能出現的情況
{
    char boardCopy[10];
    for (int i = 1; i < 10; i++)
        boardCopy[i] = board[i];
    return *boardCopy;
}

_Bool isSpaceFree(char *board,int move) //判斷棋盤上是否為空
{
    return board[move] == ' ';
}

int getPlayerMove(char *board) //讀取玩家棋子移動
{
    puts("你下一步走哪里？（1-9）");
    int move;
    do {
        move = getchar() - '0';
        if (move == '\n' - '0')
            continue;
        if (move < 1 || move > 9 || !isSpaceFree(board, move))
            puts("你下一步走哪里？（1-9）");
    }while (move < 1 || move > 9 || !isSpaceFree(board, move));
    return move;
}

int chooseRandomMoveFromList(char *board,char *movelist, int n) //隨機讀取計算機可移動的位置
{
    int possibleMove[4]; //每輪選擇最多只有四個
    int j = 0;
    for (int i = 0; i < n; i++)
        if (isSpaceFree(board, movelist[i] - '0'))
            possibleMove[j++] = movelist[i] - '0';

    if (j != 0)
        return possibleMove[rand()%j];
    else
        return 0;
}

int getComputerMove(char board[], char computerLetter) //獲得計算機的移動
{
    char playerLetter;
    char boardCopy[10];
    if (computerLetter == 'X') //根據計算機的棋子，判斷玩家棋子
        playerLetter = 'O';
    else
        playerLetter = 'X';

    for (int i = 1; i < 10; i++){ //如果下一步可獲勝，下那一步
        strcpy(boardCopy, board);
        if (isSpaceFree(boardCopy, i)) {
            makeMove(boardCopy, computerLetter,i);
                if (isWinner(boardCopy, computerLetter))
                    return i;
        }
    }

    for (int i = 1; i < 10; i++){ //如果下一步玩家會獲勝，占那個位置
        strcpy(boardCopy,board);
        if (isSpaceFree(boardCopy, i)) {
            makeMove(boardCopy, playerLetter,i);
                if (isWinner(boardCopy, playerLetter))
                    return i;
        }
    }

    int move; //如果下一步不是決勝步
    move = chooseRandomMoveFromList(board, "1379", 4); //四個角優先
    if (move != 0)
        return move;

    move = chooseRandomMoveFromList(board, "5", 1); //中間
    if (move != 0)
        return move;
    
    return chooseRandomMoveFromList(board, "2468", 4); //剩下的位置
}

_Bool isBoardFull(char *board) //判斷棋盤是否滿了
{
    for (int i = 1; i < 10; i++)
        if (isSpaceFree(board, i))
            return 0;
    return 1;
}

_Bool isAgain() //再來一局
{
    char again;
    do{
        again = tolower(getchar());
        if (again == '\n')
            continue;
        if (again != 'n' && again != 'y')
            puts("請輸入y或n。");
    }while (again != 'n' && again != 'y');
    
    if (again == 'y')
        return 1;
    else 
        return 0;
}


int main()
{
    puts("歡迎來玩井字棋！") ;

    while(1) { //游戲
        char theBoard[10];
        for (int i = 1; i < 10; i++) //將棋盤設為空白
            theBoard[i] = ' ';
        char playerLetter = inputPlayerLetter(); //獲得玩家所選的棋子
        char computerLetter = (playerLetter == 'X')?'O': 'X' ;
        //獲得計算機的棋子
        _Bool isTurnPlayer; //設定是否是玩家回合
        int move;
        srand((unsigned)time(NULL)); //隨機先后手
        if (rand() % 2) {
            isTurnPlayer = 0;
            puts("電腦先走。");
        }else {
                   isTurnPlayer = 1;
            puts("玩家先走。");
        }
        _Bool gameIsPlaying = 1; //設定游戲是否進行

        while (gameIsPlaying) {

            if (isTurnPlayer) { //如果是玩家回合
                drawBoard(theBoard);
                move = getPlayerMove(theBoard);
                makeMove(theBoard, playerLetter, move);

                if (isWinner(theBoard, playerLetter)) { //如果獲勝
                    drawBoard(theBoard);
                    puts("太棒了！你獲勝了！");
                    gameIsPlaying = 0;
                }
            
                else { //如果平局
                    if (isBoardFull(theBoard)) {
                        drawBoard(theBoard);
                        puts("平局了！");
                        break;
                    }
                    else //設定輪到計算機
                        isTurnPlayer = 0;
                }
            }

            else { //輪到計算機了
                move = getComputerMove(theBoard, computerLetter);
                makeMove(theBoard, computerLetter, move);
                if (isWinner(theBoard, computerLetter)) { //如果獲勝
                    drawBoard(theBoard);
                    puts("電腦打敗了你！你輸了。");
                    gameIsPlaying = 0;
                } else { //平局
                    if (isBoardFull(theBoard)) {
                        drawBoard(theBoard);
                        puts("平局了！");
                        break;
                    } else // 設定輪到玩家
                        isTurnPlayer = 1;
                }
            }
        }
        puts("再來一局？（yes或no）");
        if (!isAgain())
            break;
    }
    return 0;
}