1 #include<stdio.h>
 2 #define MaxSize 20
 3 typedef struct{
 4     char element[MaxSize];
 5     int top;
 6 }SeqStack;
 7 void InitStack(SeqStack*p)//初始化 
 8 {
 9     p->top=-1;
10  } 
11 void PushStack(char e,SeqStack*p)//压栈 
12 {
13     if(p->top!=MaxSize-1){
14     p->top++;
15     p->element[p->top]=e;}
16 }
17 char PopStack(SeqStack*p)//出栈 
18 {    
19     char x;
20     if(p->top!=-1){
21     x=p->element[p->top];
22     p->top--;}
23     return x;
24 }
25 int Compare(char left,char right)//比较函数 
26 {
27     int flag;
28     switch(left)
29     {
30         case '+':
31             {
32                 if(right=='-'||right==')'||right=='\n')flag=0;
33                 else if(right=='*'||right=='/'||right=='(')flag=2;
34                 break;
35             }
36         case '-':
37             {
38             if(right=='+'||right==')'||right=='\n')flag=0;
39                 else if(right=='*'||right=='/'||right=='(')flag=2;
40                 break;
41             }
42         case '*':
43         {
44             if(right=='+'||right=='-'||right=='/'||right==')'||right=='\n')flag=0;
45             else if(right=='(')flag=2;
46             break;
47          } 
48         case '/':
49              {
50             if(right=='+'||right=='-'||right=='*'||right==')'||right=='\n')flag=0;
51             else if(right=='(')flag=2;
52             break;
53          } 
54         case '(':
55             {
56                 if(right==')')flag=1;
57                 else flag=2;
58                 break;
59             }//注：只要right为')'就会不停往前Execute直至遇到'('，并最后读取下一个数据 。故')'不会被储存到b中 
60         case '\n':flag=3;break;
61         
62     }
63     return flag; 
64 }
65 void Conversation(SeqStack*a,SeqStack*b)//a存储后缀表达式，b暂时存储运算符 
66 {
67     char e,oper;
68     scanf("%c",&e);
69     while(e!='\n'||b->top!=-1)//！！不要将||写成&& 
70     {
71         if(e!='+'&&e!='-'&&e!='*'&&e!='/'&&e!='('&&e!=')'&&e!='\n')PushStack(e,a),scanf("%c",&e);
72         /* 读取到运算数则存入栈a，并继续读取 */
73         else if(b->top==-1||Compare(b->element[b->top],e)==2)PushStack(e,b),scanf("%c",&e);
74         /* 读取到运算符，当b栈为空或当前运算符优先级大于b栈首，入栈b，并继续读取 */
75         else if(Compare(b->element[b->top],e)==1)PopStack(b),scanf("%c",&e);
76         /* 读取到')',当')'遇到'(',将'('弹出栈b,并继续读取 */ 
77         else if(Compare(b->element[b->top],e)==0)
78         {
79             oper=PopStack(b);
80             PushStack(oper,a);
81          } 
82          /* 读取到运算符，当运算符优先级低于b栈首，弹出b栈首并存入到a中，继续比较当前运算符 */ 
83     }
84 }
85 int main()
86 {
87     SeqStack A,B;
88     SeqStack*a,*b;
89     a=&A,b=&B;
90     InitStack(a),InitStack(b);
91     Conversation(a,b);
92     a->top++,a->element[a->top]='\n';
93     for(int i=0;a->element[i]!='\n';i++)printf("%c",a->element[i]);
94     return 0;
95  }