中缀表达式转换成后缀表达式

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #define STACK_INIT_SIZE 20
  4 #define STACK_INCREMENT 10
  5 typedef char ElemType;
  6 typedef char Status;
  7 
  8 typedef struct
  9 {
 10     ElemType *base;
 11     ElemType *top;
 12     int stacksize;
 13 }SqStack;
 14 
 15 Status InitStack( SqStack *S )
 16 {
 17     S->base = ( ElemType *) malloc (  STACK_INIT_SIZE*sizeof( ElemType ) );
 18     S->top  = S->base ;
 19     S->stacksize = STACK_INIT_SIZE;
 20 
 21     return 0;
 22 }
 23 
 24 //插入元素e,即入栈
 25 Status Push( SqStack *S , ElemType e )
 26 {
 27     if ( S->top - S->base >= S->stacksize )  //当前容量大于或等于最大容量
 28     {
 29     //追加栈的空间
 30     S->base = ( ElemType *) realloc ( S->base,  S->stacksize + STACK_INCREMENT*sizeof( ElemType ) );
 31     if ( !S->base )
 32         return  -1;
 33     S->top = S->base  + S->stacksize ;
 34     S->stacksize = S->stacksize + STACK_INCREMENT;
 35 
 36     }
 37     //开始赋值
 38     *S->top = e;
 39     S->top++;
 40 
 41     return 0;                              //注意返回值为0，不是e
 42 }
 43 
 44 //弹出元素e，即出栈
 45 Status Pop ( SqStack *S , ElemType *e )//此处S为结构体指针的变量，所以访问结构体成员用"->"
 46 {
 47     //首先判断栈内是否为空
 48     if ( S->top == S->base )
 49     return -1 ;
 50 
 51     --S->top ;
 52     *e = *S->top ;
 53 
 54     return *e;                         //注意返回值为e，不是0
 55 }
 56 
 57 int StackLen ( SqStack S )//S为结构体变量，所以访问结构体成员用"."
 58 {
 59     return  ( S.top - S.base );
 60 }
 61 
 62 int main()
 63 {
 64    SqStack s;
 65    char c,e;
 66    InitStack(&s);
 67    printf("请按中缀表达式输入式子，以‘#‘作为结束符：\n");
 68    scanf("%c",&c);
 69    while(c!=‘#‘)
 70    {
 71        while(c>=‘0‘&&c<=‘9‘)
 72        {
 73            printf("%c",c);
 74            scanf("%c",&c);
 75            if(c<‘0‘||c>‘9‘)
 76            {
 77                printf(" ");
 78            }
 79        }
 80            if(‘)‘==c)
 81            {
 82                 Pop(&s,&e);
 83                 while(‘(‘!=e)
 84                 {
 85                     printf("%c ",e);
 86                     Pop(&s,&e);
 87                 }
 88            }
 89            else if(‘+‘==c||‘-‘==c)
 90            {
 91                if(!StackLen(s))
 92                {
 93                    Push(&s,c);
 94                }
 95                else
 96                {
 97                    do
 98                    {
 99                        Pop(&s,&e);
100                        if(‘(‘==e)
101                        {
102                            Push(&s,e);
103                        }
104                        else
105                        {
106                            printf("%c ",e);
107                        }
108                    }while(StackLen(s)&&‘(‘!=e);
109                    Push(&s,c);
110                }
111            }
112 
113            else if(‘*‘==c||‘/‘==c||‘(‘==c)
114            {
115                 Push(&s,c);
116            }
117            else if(‘#‘==c)
118            {
119                break;
120            }
121            else
122            {
123                printf("\n 出错");
124                return -1;
125            }
126            scanf("%c",&c);
127    }
128        while(StackLen(s))
129        {
130            Pop(&s,&e);
131            printf("%c ",e);
132        }
133    return 0;
134 }