运算字符串解析（c语言）

运算字符的解析，如：43+表示：4+3， 25* 表示：2*5， 25*1+表示（2*5）+1，435/+表示：4 +（3/5）

 1 #include <stdio.h>

 2 #include <stdbool.h>

 3 #include <string.h>

 4 

 5 bool isNumber(const char *c);

 6 int getNumber(const char *c);

 7 bool isOperator(const char *c);

 8 float calculate(char *string, int len);

 9 

10 int main(int argc, const char * argv[])

11 {

12 

13     // insert code here...

14     printf("Begin>>\n");

15     printf("%d",'0');

16     printf("%d\n",'/');

17     char string[100] = "435/+";

18     size_t len = strlen(string);

19     float ret = calculate(string, (int)len);

20     printf("result = %f\n", ret);

21     return 0;

22 }

23 

24 bool isNumber(const char *c)

25 {

26     if ( (int)(*c) >= (int)('0') && (int)(*c) <= (int)('9')) {

27         return true;

28     }

29     return false;

30 }

31 

32 int getNumber(const char *c)

33 {

34     bool isN = isNumber(c);

35     if (isN) {

36         int n = (int)((*c) - (int)'0');

37         return n;

38     }else {

39         return 0;

40     }

41 }

42 

43 bool isOperator(const char *c)

44 {

45     if ((int)(*c) == (int)'+' || (int)(*c) == (int)'-' || (int)(*c) == (int)('*') || (int)(*c) == (int)('/') ) {

46         return true;

47     } else {

48         return false;

49     }

50     

51 }

52 

53 float calculate(char *string, int len)

54 {

55     if (len == 1) {

56         return (float)getNumber(string);

57     }

58     

59     if (len == 2) {

60         printf("error!");

61     }

62     

63     if (!isOperator(string + len - 1)) {

64         return 0.0f;

65     }

66     

67     float a = 0.0f;

68     float b = 0.0f;

69     if (isOperator(string + len - 1 -1)) {

70         a = (float)getNumber(string);

71         b = calculate(string + 1, len - 2);

72     } else {

73         a = calculate(string, len - 2);

74         b = (float)getNumber(string + len - 1 - 1);

75     }

76     

77     char operator = *(string + len - 1);

78     if ((int)operator == (int)'+') {

79         return (a + b);

80     } else if ((int)operator == (int)'-') {

81         return (a - b);

82     } else if ((int)operator == (int)'*') {

83         return (a * b);

84     } else if ((int)operator == (int)'/') {

85         return (a / b);

86     } else {

87         return 0.0f;

88     }

89     

90 }