劣质代码评析——《写给大家看的C语言书（第2版）》附录B之21点程序（四）

0. #include <stdio.h>

1. #include <time.h>

2. #include <ctype.h>

3. #include <stdlib.h>

4. 

5. #define BELL '\a'

6. #define DEALER 0

7. #define PLAYER 1

8. 

9. #define ACELOW 0

10. #define ACEHIGH 1

11. 

12. int askedForName = 0;

13. 

14. 

15. void dispTitle(void);

16. void initCardsScreen(int cards[52],int playerPoints[2],

17. int dealerPoints[2], int total[2], 

18. int *numCards);

19. int dealCard(int * numCards,int cards[52]);

20. void dispCard(int cardDrawn,int points[2]);

21. void totalIt(int points[2],int tatal[2],int who);

22. void dealerGetsCard(int *numCards,int cards[52],

23. int dealerPoints[2]);

24. void playerGetsCard(int *numCards,int cards[52],

25. int playerPoints[2]);

26. char getAns(char mesg[]);

27. void findWinner(int total[2]);

28. 

29. main()

30. {

31.    int numCards;

32.    int cards[52],playerPoints[2],dealerPoints[2],total[2];

33.    char ans;

34.    

35.    do 

36.    { 

37.       initCardsScreen(cards,playerPoints,dealerPoints,total, &numCards);

38.       dealerGetsCard(&numCards,cards, dealerPoints);

39.       printf("\n");

40.       playerGetsCard(&numCards,cards,playerPoints); 

41.       playerGetsCard(&numCards,cards,playerPoints);

42.       do

43.       {

44.          ans = getAns("Hit or stand (H/S)?");

45.          if ( ans == 'H' )

46.          { 

47.             playerGetsCard(&numCards,cards,playerPoints);

48.          }  

49.       }

50.       while( ans != 'S' );

51.       

52.       totalIt(playerPoints,total,PLAYER);

53.       do

54.       {

55.          dealerGetsCard(&numCards,cards,dealerPoints);

56.       }

57.       while (dealerPoints[ACEHIGH] < 17 );

58.       

59.       totalIt(dealerPoints,total,DEALER);

60.       findWinner(total); 

61.       

62.       ans = getAns("\nPlay again(Y/N)?");  

63.    }

64.    while(ans=='Y');

65.    

66.    return 0;

67. }

68. 

69. void initCardsScreen( int cards[52],int playerPoints[2],

70.                       int dealerPoints[2], int total[2], 

71.                       int *numCards )

72. {

73.    int sub,val = 1 ;

74.    char firstName[15];

75.    *numCards=52;

76.    

77.    for(sub=0;sub<=51;sub++)

78.    {

79.       val = (val == 14) ? 1 : val;

80.       cards[sub] = val;

81.       val++;  

82.    }

83.    

84.    for(sub=0;sub<=1;sub++)

85.    { 

86.       playerPoints[sub]=dealerPoints[sub]=total[sub]=0;

87.    }

88.    dispTitle();

89.    

90.    if (askedForName==0)

91.    { 

92.       printf("What is your first name?");

93.       scanf(" %s",firstName);

94.       askedForName=1;

95.       printf("Ok, %s,get ready for casino action!\n\n",firstName);

96.       getchar();

97.    }

98.    return;        

99. }

100. 

101. void playerGetsCard(int *numCards,int cards[52],int playerPoints[2])

102. {

103.    int newCard;

104.    newCard = dealCard(numCards, cards);

105.    printf("You draw:");

106.    dispCard(newCard,playerPoints);

107. }

108. 

109. 

110. void dealerGetsCard(int *numCards,int cards[52],int dealerPoints[2])

111. {

112.    int newCard;

113.    newCard = dealCard(numCards,cards);

114.    printf("The dealer draws:");

115.    dispCard(newCard,dealerPoints);

116. }

117. 

118. int dealCard(int * numCards,int cards[52])

119. {

120.    int cardDrawn,subDraw;

121.    time_t t;

122.    srand(time(&t));

123.    subDraw = (rand()%(*numCards));

124.    cardDrawn = cards[subDraw];

125.    cards[subDraw] = cards[*numCards -1];

126.    (*numCards)--;

127.    return cardDrawn;

128. }

129. 

130. void dispCard(int cardDrawn, int points[2])

131. {

132.    switch(cardDrawn)

133.    {

134.       case(11): printf("%s\n","Jack");

135.                 points[ACELOW] += 10;

136.                 points[ACEHIGH] += 10;

137.                 break;

138.       case(12): printf("%s\n","Queen");

139.                 points[ACELOW] += 10;

140.                 points[ACEHIGH] += 10;

141.                 break;

142.       case(13): printf("%s\n","King");

143.                 points[ACELOW] += 10;

144.                 points[ACEHIGH] += 10;

145.                 break;

146.       default : points[ACELOW] += cardDrawn;

147.                 if(cardDrawn==1)

148.                 { 

149.                    printf("%s\n","Ace");

150.                    points[ACEHIGH]+= 11;

151.                 }

152.                 else

153.                 {  

154.                   points[ACEHIGH]+=cardDrawn;

155.                   printf("%d\n",cardDrawn); 

156.                 }

157.    }

158.    return ;

159. }

160. 

161. void totalIt(int points[2],int total[2],int who)

162. {

163.    if ( (points[ACELOW] == points[ACEHIGH])

164.       ||(points[ACEHIGH] < 21 ))

165.    { 

166.      total[who] = points[ACELOW];

167.    }

168.    else

169.    { 

170.        total[who] = points[ACEHIGH];

171.    }

172.    

173.    if (who == PLAYER )

174.    {

175.       printf("You have a total of %d\n\n", total[PLAYER]);

176.    }

177.    else

178.    {

179.        printf("The house stands with a total of %d\n\n", 

180.        total[DEALER]);

181.    }

182.    return;

183. }

184. 

185. void findWinner(int total[2])

186. {

187.    if ( total[DEALER] ==  21 )

188.    {

189.        printf("The house wins.\n");

190.        return ;

191.    }

192.    if ( (total[DEALER] > 21) && (total[PLAYER] > 21) )

193.    { 

194.       printf("%s", "Nobody wins.\n");

195.       return ; 

196.    }

197.    if ((total[DEALER] >= total[PLAYER])&& (total[DEALER] < 21))

198.    { 

199.       printf("The house wins.\n");

200.       return ; 

201.    }

202.    printf("%s%c","You win!\n",BELL);

203.    return;

204. }

205. 

206. char getAns(char mesg[])

207. {

208.    char ans;

209.    printf("%s", mesg);

210.    ans = getchar();

211.    getchar();

212.    return toupper(ans);

213. }

214. 

215. void dispTitle(void)

216. {

217.    int i = 0 ;

218.    while(i<25)

219.    { 

220.         printf("\n");

221.         i++; 

222.    }

223.    printf("\n\n*Step right up to the Blackjack tables*\n\n");

224.    return ;

225. }

View Code

29. main()

30. {

31.    int numCards;

32.    int cards[52],playerPoints[2],dealerPoints[2],total[2];

33.    char ans;

34.    

35.    do 

36.    { 

37.       initCardsScreen(cards,playerPoints,dealerPoints,total, &numCards);

38.       dealerGetsCard(&numCards,cards, dealerPoints);

39.       printf("\n");

40.       playerGetsCard(&numCards,cards,playerPoints); 

41.       playerGetsCard(&numCards,cards,playerPoints);

42.       do

43.       {

44.          ans = getAns("Hit or stand (H/S)?");

45.          if ( ans == 'H' )

46.          { 

47.             playerGetsCard(&numCards,cards,playerPoints);

48.          }  

49.       }

50.       while( ans != 'S' );

51.       

52.       totalIt(playerPoints,total,PLAYER);

53.       do

54.       {

55.          dealerGetsCard(&numCards,cards,dealerPoints);

56.       }

57.       while (dealerPoints[ACEHIGH] < 17 );

58.       

59.       totalIt(dealerPoints,total,DEALER);

60.       findWinner(total); 

61.       

62.       ans = getAns("\nPlay again(Y/N)?");  

63.    }

64.    while(ans=='Y');

65.    

66.    return 0;

67. }

　　现在回到main()继续代码走查。

   38.       dealerGetsCard(&numCards,cards, dealerPoints);

 　　这句话的意图是实现计算机（作为dealer）抽一张牌，并且这张牌的点数两个游戏者能看得见。其函数类型声明为： 

    22. void dealerGetsCard(int *numCards,int cards[52],

    23. int dealerPoints[2]);

 　　这个函数类型声明写得同样很不地道，原因前面提到过，这里不再复述。应该把它改为： 

    void dealerGetsCard ( int *numCards , int cards[] , int dealerPoints[] );

　　该函数的函数定义为： 

    110. void dealerGetsCard(int *numCards,int cards[52],int dealerPoints[2])

    111. {

    112.    int newCard;

    113.    newCard = dealCard(numCards,cards);

    114.    printf("The dealer draws:");

    115.    dispCard(newCard,dealerPoints);

    116. }

 　　有不少初学者不定义几个根本没必要的变量就不会写代码，这个函数犯的也是这种幼稚病。

　　newCard这个变量明显多余。此外函数的头部也需要修改。形参numCards名字的毛病这里暂时就不改了： 

    void dealerGetsCard(int *numCards,int cards[],int dealerPoints[])

    {

       printf("The dealer draws:");

       dispCard ( dealCard( numCards , cards ) , dealerPoints ) ;

    }

 　　这里又涉及到了dealCard()函数和dispCard()，先来看dealCard()函数。

    19. int dealCard(int * numCards,int cards[52]);

    

    

    118. int dealCard(int * numCards,int cards[52])

    119. {

    120.    int cardDrawn,subDraw;

    121.    time_t t;

    122.    srand(time(&t));

    123.    subDraw = (rand()%(*numCards));    /* From 0 to numcards */

    124.    cardDrawn = cards[subDraw];

    125.    cards[subDraw] = cards[*numCards -1];

    126.    (*numCards)--;

    127.    return cardDrawn;

    128. }

 　　函数原型方面的问题这里就不再提了。

　　这个函数中有这样两层意思，首先在剩下的牌（共* numcards 张）中随机确定一张牌(第subDraw张)，然后再模拟把这张牌从整副牌中抽走（cards[subDraw] = cards[*numCards -1]; (*numCards)--;）。

　　这个函数有这样一些错误和毛病： 

    121.    time_t t;

 　　这个变量定义是毫无意义的，后面进一步说明。 

    122.    srand(time(&t));

 　　此函数调用的目的是设置伪随机数的种子（Seed），其中有两个错误：

　　第一，&t作为实参是毫无必要的。因为这里只需要time()函数的返回值，而不需要通过变量t保存并带回时间的值。这时的代码应该这样写

    srand( time ( NULL ) );

　　第二个错误是，需要得到伪随机数列时，只需要在最初设置一次种子，而不是反复设置种子。也就是说这个srand()只需要在每次游戏的初期调用一次，以后则毋庸再调用。那么，很显然，这个函数调用绝对不应该出现在dealCard()这个函数中，而应该出现在main()函数的do-while语句之中，如下面所示。 

    int main(void)

    {

       /*……*/

    

       do{

            srand( time ( NULL ) );

            /*21点游戏*/

        }

       while( getAns("\nPlay again(Y/N)?") == 'Y' );  /*询问是否继续*/

    

        return 0;

    }

　　dealCard()函数中的 

   123.    subDraw = ( rand() % (*numCards) );    /* From 0 to numcards */

 　　代码本身没有问题，但注释是错误的。作者忘记了numcards在这个函数中是一个指针，而且rand() % (*numCards) 所能得到的值只可能在 0 ~ (*numCards)-1 这个范围。

　　这个函数的返回值即为抽到的牌的点数，这个点数作为实参调用dispCard ()函数。即

    dispCard ( dealCard( numCards , cards ) , dealerPoints ) ;

    //原115.    dispCard(newCard,dealerPoints);

（未完待续）