1 #include<stdio.h>
2 #include<stdlib.h>
3 #define Stack_Size 100
4 #define StackIncrement 10
5 #define Ok 1
6 #define Error 0
7 #define Overflow -2
8 #define True 1
9 #define False -1
10 typedef int status;
11 //数字栈的操作
12 typedef struct
13 {
14 float *base;
15 float *top;
16 int stacksize;
17 }SqStack;
18 status InitStack(SqStack &S)
19 {
20 S.base=(float *)malloc(Stack_Size*sizeof(float));
21 if(!S.base) exit(False);
22 S.top=S.base;
23 S.stacksize=Stack_Size;
24 return Ok;
25 }
26 status StackEmpty(SqStack &S)
27 {
28 if(S.top==S.base)
29 return True;
30 return Error;
31 }
32 float GetTop(SqStack S)
33 {
34 float e;
35 if(S.top==S.base) return Error;
36 e=*(S.top-1);
37 return e;
38 }
39 status Push(SqStack &S,float e)
40 {
41 if((S.top-S.base)==S.stacksize)
42 {
43 S.base=(float *)realloc(S.base,(S.stacksize+StackIncrement)*sizeof(float));
44 if(!S.base) exit(False);
45 S.top=S.base+S.stacksize;
46 S.stacksize+=StackIncrement;
47 }
48 *S.top++=e;
49 return Ok;
50 }
51 status Pop(SqStack &S,float &e)
52 {
53 if(S.top==S.base) return Error;
54 e=*--S.top;
55 return Ok;
56 }
57 //转化的操作过程
58 float Operate(float a,char theta,float b)
59 {
60 switch(theta)
61 {
62 case '+': return a+b;
63 case '-': return a-b;
64 case '*': return a*b;
65 case '/': return a/b;
66 default: return Error;
67 }
68 }
69 status In(char c)
70 {
71 switch(c)
72 {
73 case '#':
74 case ')':
75 case '+':
76 case '-':
77 case '*':
78 case '/':
79 case '(': return True;
80 case ' ': return False;
81 default : return Error;
82 }
83 }
84 float Evaluateexpression_r(char *S)
85 {
86 SqStack OPND;InitStack(OPND);
87 float a,b; int k; char *p=S;
88 char c=*p;
89 while(c!='#')
90 {
91 if(!In(c))
92 {
93 for(k=0;In(c)!=-1;c=*++p)
94 k=10*k+c-'0';
95 Push(OPND,k);
96 }
97 else
98 {
99 Pop(OPND,b); Pop(OPND,a);
100 Push(OPND,Operate(a,c,b));
101 }
102 c=*++p;
103 }
104 return GetTop(OPND);
105 }
106 //主函数
107 status main()
108 {
109 char S[100];
110 float result;
111 puts("请输入后缀表达式:");
112 gets(S);
113 result=Evaluateexpression_r(S);
114 printf("%.2f\n",result);
115 return Ok;
116 }
