要是先手，先下中间一颗，那电脑只有四种情况赢了 哈哈

估计大部分是和局

#include <stdio.h>
#include <bios.h>
#include <ctype.h>
#include <conio.h>
#include <dos.h>
#define CROSSRU 0xbf /*右上角点*/
#define CROSSLU 0xda /*左上角点*/
#define CROSSLD 0xc0 /*左下角点*/
#define CROSSRD 0xd9 /*右下角点*/
#define CROSSL 0xc3 /*左边*/
#define CROSSR 0xb4 /*右边*/
#define CROSSU 0xc2 /*上边*/
#define CROSSD 0xc1 /*下边*/
#define CROSS 0xc5 /*十字交叉点*/

/*定义棋盘左上角点在屏幕上的位置*/
#define MAPXOFT 5
#define MAPYOFT 2

/*定义1号玩家的操作键键码*/
#define PLAY1UP 0x1157/*上移--'W'*/
#define PLAY1DOWN 0x1f53/*下移--'S'*/
#define PLAY1LEFT 0x1e41/*左移--'A'*/
#define PLAY1RIGHT 0x2044/*右移--'D'*/
#define PLAY1DO 0x3920/*落子--空格键*/

/*定义2号玩家的操作键键码*/
#define PLAY2UP 0x4800/*上移--方向键up*/
#define PLAY2DOWN 0x5000/*下移--方向键down*/
#define PLAY2LEFT 0x4b00/*左移--方向键left*/
#define PLAY2RIGHT 0x4d00/*右移--方向键right*/
#define PLAY2DO 0x1c0d/*落子--回车键Enter*/

/*若想在游戏中途退出, 可按 Esc 键*/
#define ESCAPE 0x011b

/*定义棋盘上交叉点的状态, 即该点有无棋子 */
/*若有棋子, 还应能指出是哪个玩家的棋子 */
#define CHESSNULL 0 /*没有棋子*/
#define CHESS1 'O'/*一号玩家的棋子*/
#define CHESS2 'X'/*二号玩家的棋子*/

/*定义按键类别*/
#define KEYEXIT 0/*退出键*/
#define KEYFALLCHESS 1/*落子键*/
#define KEYMOVECURSOR 2/*光标移动键*/
#define KEYINVALID 3/*无效键*/

/*定义符号常量: 真, 假 --- 真为1, 假为0 */
#define TRUE 1
#define FALSE 0

/**********************************************************/
/* 定义数据结构 */

/*棋盘交叉点坐标的数据结构*/
struct point
{
int x,y;
};

/**********************************************************/
/*自定义函数原型说明 */
void Init(void);
int GetKey(void);
int CheckKey(int press);
int ChangeOrder(void);
int ChessGo(int Order,struct point Cursor);
void DoError(void);
void DoOK(void);
void DoWin(int Order);
void MoveCursor(int Order,int press);
void DrawCross(int x,int y);
void DrawMap(void);
int JudgeWin(int Order,struct point Cursor);
int JudgeWinLine(int Order,struct point Cursor,int direction);
void ShowOrderMsg(int Order);
void EndGame(void);
/**********************************************************/

/**********************************************************/
/* 定义全局变量 */
int gPlayOrder; /*指示当前行棋方 */
struct point gCursor; /*光标在棋盘上的位置 */
char gChessBoard[19][19];/*用于记录棋盘上各点的状态*/
/**********************************************************/

/**********************************************************/
/*主函数*/
void main()
{
int press;
int bOutWhile=FALSE;/*退出循环标志*/

Init();/*初始化图象，数据*/

while(1)
{
press=GetKey();/*获取用户的按键值*/
switch(CheckKey(press))/*判断按键类别*/
{
/*是退出键*/
case KEYEXIT:
clrscr();/*清屏*/
bOutWhile = TRUE;
break;

/*是落子键*/
case KEYFALLCHESS:
if(ChessGo(gPlayOrder,gCursor)==FALSE)/*走棋*/
DoError();/*落子错误*/
else
{
DoOK();/*落子正确*/

/*如果当前行棋方赢棋*/
if(JudgeWin(gPlayOrder,gCursor)==TRUE)
{
DoWin(gPlayOrder);
bOutWhile = TRUE;/*退出循环标志置为真*/
}
/*否则*/
else
/*交换行棋方*/
ChangeOrder();
ShowOrderMsg(gPlayOrder);
}
break;

/*是光标移动键*/
case KEYMOVECURSOR:
MoveCursor(gPlayOrder,press);
break;

/*是无效键*/
case KEYINVALID:
break;
}

if(bOutWhile==TRUE)
break;
}

/*游戏结束*/
EndGame();
}
/**********************************************************/

/*界面初始化，数据初始化*/
void Init(void)
{
int i,j;
char *Msg[]=
{
"Player1 key:",
" UP----w",
" DOWN--s",
" LEFT--a",
" RIGHT-d",
" DO----space",
"",
"Player2 key:",
" UP----up",
" DOWN--down",
" LEFT--left",
" RIGHT-right",
" DO----ENTER",
"",
"exit game:",
" ESC",
NULL,
};

/* 先手方为1号玩家 */
gPlayOrder = CHESS1;
/* 棋盘数据清零, 即棋盘上各点开始的时候都没有棋子 */
for(i=0;i<19;i++)
for(j=0;j<19;j++)
gChessBoard[i][j]=CHESSNULL;
/*光标初始位置*/
gCursor.x=gCursor.y=0;

/*画棋盘*/
textmode(C40);
DrawMap();

/*显示操作键说明*/
i=0;
textcolor(BROWN);
while(Msg[i]!=NULL)
{
gotoxy(25,3+i);
cputs(Msg[i]);
i++;
}

/*显示当前行棋方*/
ShowOrderMsg(gPlayOrder);
/*光标移至棋盘的左上角点处*/
gotoxy(gCursor.x+MAPXOFT,gCursor.y+MAPYOFT);
}

/*画棋盘*/
void DrawMap(void)
{
int i,j;

clrscr();

for(i=0;i<19;i++)
for(j=0;j<19;j++)
DrawCross(i,j);

}

/*画棋盘上的交叉点*/
void DrawCross(int x,int y)
{
gotoxy(x+MAPXOFT,y+MAPYOFT);
/*交叉点上是一号玩家的棋子*/
if(gChessBoard[x][y]==CHESS1)
{
textcolor(LIGHTBLUE);
putch(CHESS1);
return;
}
/*交叉点上是二号玩家的棋子*/
if(gChessBoard[x][y]==CHESS2)
{
textcolor(LIGHTBLUE);
putch(CHESS2);
return;
}

textcolor(GREEN);

/*左上角交叉点*/
if(x==0&&y==0)
{
putch(CROSSLU);
return;
}

/*左下角交叉点*/
if(x==0&&y==18)
{
putch(CROSSLD);
return;
}

/*右上角交叉点*/
if(x==18&&y==0)
{
putch(CROSSRU);
return;
}

/*右下角交叉点*/
if(x==18&&y==18)
{
putch(CROSSRD);
return;
}

/*左边界交叉点*/
if(x==0)
{
putch(CROSSL);
return;
}

/*右边界交叉点*/
if(x==18)
{
putch(CROSSR);
return;
}

/*上边界交叉点*/
if(y==0)
{
putch(CROSSU);
return;
}

/*下边界交叉点*/
if(y==18)
{
putch(CROSSD);
return;
}

/*棋盘中间的交叉点*/
putch(CROSS);
}

/*交换行棋方*/
int ChangeOrder(void)
{
if(gPlayOrder==CHESS1)
gPlayOrder=CHESS2;
else
gPlayOrder=CHESS1;

return(gPlayOrder);
}

/*获取按键值*/
int GetKey(void)
{
char lowbyte;
int press;

while (bioskey(1) == 0)
;/*如果用户没有按键，空循环*/

press=bioskey(0);
lowbyte=press&0xff;
press=press&0xff00 + toupper(lowbyte);
return(press);
}

/*落子错误处理*/
void DoError(void)
{
sound(1200);
delay(50);
nosound();
}

/*赢棋处理*/
void DoWin(int Order)
{
sound(1500);delay(100);
sound(0); delay(50);
sound(800); delay(100);
sound(0); delay(50);
sound(1500);delay(100);
sound(0); delay(50);
sound(800); delay(100);
sound(0); delay(50);
nosound();

textcolor(RED+BLINK);
gotoxy(25,20);
if(Order==CHESS1)
cputs("PLAYER1 WIN!");
else
cputs("PLAYER2 WIN!");
gotoxy(25,21);
cputs("\n");
getch();
}

/*走棋*/
int ChessGo(int Order,struct point Cursor)
{
/*判断交叉点上有无棋子*/
if(gChessBoard[Cursor.x][Cursor.y]==CHESSNULL)
{
/*若没有棋子, 则可以落子*/
gotoxy(Cursor.x+MAPXOFT,Cursor.y+MAPYOFT);
textcolor(LIGHTBLUE);
putch(Order);
gotoxy(Cursor.x+MAPXOFT,Cursor.y+MAPYOFT);
gChessBoard[Cursor.x][Cursor.y]=Order;
return TRUE;
}
else
return FALSE;
}

/*判断当前行棋方落子后是否赢棋*/
int JudgeWin(int Order,struct point Cursor)
{
int i;
for(i=0;i<4;i++)
/*判断在指定方向上是否有连续5个行棋方的棋子*/
if(JudgeWinLine(Order,Cursor,i))
return TRUE;
return FALSE;
}

/*判断在指定方向上是否有连续5个行棋方的棋子*/
int JudgeWinLine(int Order,struct point Cursor,int direction)
{
int i;
struct point pos,dpos;
const int testnum = 5;
int count;

switch(direction)
{
case 0:/*在水平方向*/
pos.x=Cursor.x-(testnum-1);
pos.y=Cursor.y;
dpos.x=1;
dpos.y=0;
break;
case 1:/*在垂直方向*/
pos.x=Cursor.x;
pos.y=Cursor.y-(testnum-1);
dpos.x=0;
dpos.y=1;
break;
case 2:/*在左下至右上的斜方向*/
pos.x=Cursor.x-(testnum-1);
pos.y=Cursor.y+(testnum-1);
dpos.x=1;
dpos.y=-1;
break;
case 3:/*在左上至右下的斜方向*/
pos.x=Cursor.x-(testnum-1);
pos.y=Cursor.y-(testnum-1);
dpos.x=1;
dpos.y=1;
break;
}

count=0;
for(i=0;i<testnum*2+1;i++)/*????????i<testnum*2-1*/
{
if(pos.x>=0&&pos.x<=18&&pos.y>=0&&pos.y<=18)
{
if(gChessBoard[pos.x][pos.y]==Order)
{
count++;
if(count>=testnum)
return TRUE;
}
else
count=0;
}
pos.x+=dpos.x;
pos.y+=dpos.y;
}

return FALSE;
}

/*移动光标*/
void MoveCursor(int Order,int press)
{
switch(press)
{
case PLAY1UP:
if(Order==CHESS1&&gCursor.y>0)
gCursor.y--;
break;
case PLAY1DOWN:
if(Order==CHESS1&&gCursor.y<18)
gCursor.y++;
break;
case PLAY1LEFT:
if(Order==CHESS1&&gCursor.x>0)
gCursor.x--;
break;
case PLAY1RIGHT:
if(Order==CHESS1&&gCursor.x<18)
gCursor.x++;
break;

case PLAY2UP:
if(Order==CHESS2&&gCursor.y>0)
gCursor.y--;
break;
case PLAY2DOWN:
if(Order==CHESS2&&gCursor.y<18)
gCursor.y++;
break;
case PLAY2LEFT:
if(Order==CHESS2&&gCursor.x>0)
gCursor.x--;
break;
case PLAY2RIGHT:
if(Order==CHESS2&&gCursor.x<18)
gCursor.x++;
break;
}

gotoxy(gCursor.x+MAPXOFT,gCursor.y+MAPYOFT);
}

/*游戏结束处理*/
void EndGame(void)
{
textmode(C80);
}

/*显示当前行棋方*/
void ShowOrderMsg(int Order)
{
gotoxy(6,MAPYOFT+20);
textcolor(LIGHTRED);
if(Order==CHESS1)
cputs("Player1 go!");
else
cputs("Player2 go!");

gotoxy(gCursor.x+MAPXOFT,gCursor.y+MAPYOFT);
}

/*落子正确处理*/
void DoOK(void)
{
sound(500);
delay(70);
sound(600);
delay(50);
sound(1000);
delay(100);
nosound();
}

/*检查用户的按键类别*/
int CheckKey(int press)
{
if(press==ESCAPE)
return KEYEXIT;/*是退出键*/

else
if
( ( press==PLAY1DO && gPlayOrder==CHESS1) ||
( press==PLAY2DO && gPlayOrder==CHESS2)
)
return KEYFALLCHESS;/*是落子键*/

else
if
( press==PLAY1UP || press==PLAY1DOWN ||
press==PLAY1LEFT || press==PLAY1RIGHT ||
press==PLAY2UP || press==PLAY2DOWN ||
press==PLAY2LEFT || press==PLAY2RIGHT
)
return KEYMOVECURSOR;/*是光标移动键*/

else
return KEYINVALID;/*按键无效*/
}