Add Binary

Question：

Given two binary strings, return their sum (also a binary string).

For example,

a = "11"

b = "1"

Return "100"

Solution：

 1 #define MAX_STR_LEN    (1000)

 2 void add_binary(char *s, char *s1, char *s2)

 3 {

 4     int i;

 5     int l, l1, l2;

 6     int tmp;

 7     char x[ MAX_STR_LEN ];

 8 

 9     l1 = strlen(s1);

10     l2 = strlen(s2);

11     l = 0;

12     tmp = 0;

13     memset(x, 0x00, sizeof(x));

14     while(l1 > 0 && l2 > 0)

15     {

16         tmp = s1[--l1] + s2[--l2] + tmp - 2 * '0'; 

17         switch(tmp)

18         {

19             case 0:

20                 tmp = 0;

21                 x[l++] = '0';

22                 break;

23             case 1:

24                 tmp = 0;

25                 x[l++] = '1';

26                 break;

27             case 2:

28                 tmp = 1;

29                 x[l++] = '0';

30                 break;

31             case 3:

32                 tmp = 1;

33                 x[l++] = '1';

34                 break;

35             default:

36                 printf("xxx err\n");

37                 break;

38         }

39     }

40     while(l1 > 0)

41     {

42         tmp = s1[--l1] + tmp - '0';

43         if(tmp == 0)

44         {

45             tmp = 0;

46             x[l++] = '0';

47         }

48         else if (tmp == 1)

49         {

50             tmp = 0;

51             x[l++] = '1';

52         }

53         else /* tmp == 2 */

54         {

55             tmp = 1;

56             x[l++] = '0';

57         }

58    

59     }

60     while(l2 > 0)

61     {

62         tmp = s2[--l2] + tmp - '0';

63         if(tmp == 0)

64         {

65             tmp = 0;

66             x[l++] = '0';

67         }

68         else if (tmp == 1)

69         {

70             tmp = 0;

71             x[l++] = '1';

72         }

73         else /* tmp == 2 */

74         {

75             tmp = 1;

76             x[l++] = '0';

77         }

78     }

79     if(tmp)

80         x[l++] = '1';

81     for(i = 0; i < l; i++)

82     {

83         s[l-i-1] = x[i];

84         //s[i] = x[i];

85     }

86 } 

 

Extension：

大数加法：

 1 #define MAX_STR_LEN    (1000)

 2 void add_large_number(char *s, char *s1, char *s2)

 3 {

 4     char x[MAX_STR_LEN ];

 5     int l1, l2, l;

 6     int i, tmp, carry;

 7     

 8     l1 = strlen(s1);

 9     l2 = strlen(s2);

10     carry = 0;

11     l = 0;

12     

13     while(l1 > 0 && l2 > 0)

14     {

15         tmp = s1[--l1] + s2[--l2] - 2 * '0' + carry;

16         if(tmp < 10)

17         {

18             carry = 0;

19             x[l++] = tmp + '0';

20         }

21         else

22         {

23             carry = 1;

24             x[l++] = tmp % 10 + '0';

25         }

26     }

27     while(l1 > 0)

28     {

29         tmp = s1[--l1] - '0' + carry;

30         if(tmp < 10)

31         {

32             x[l++] = tmp + '0';

33             carry = 0;    

34         }

35         else

36         {

37             x[l++] = tmp % 10 + '0';

38             carry = 1;    

39         }

40     }

41     while(l2 > 0)

42     {

43         tmp = s2[--l2] - '0' + carry;

44         if(tmp < 10)

45         {

46             x[l++] = tmp + '0';

47             carry = 0;    

48         }

49         else

50         {

51             x[l++] = tmp % 10 + '0';

52             carry = 1;    

53         }        

54     }

55     if(carry)

56     {

57         x[l++] = '1';

58     }

59     

60     for(i = 0; i < l; i++)

61     {

62         s[l-i-1] = x[i];

63         //s[i] = x[i];

64     }

65     s[l] = '\0';

66 }