C++利用栈实现中缀表达式转后缀表达式

#include <stdio.h>
#include <stdlib.h>
 
#define STACK_INIT_SIZE 20
#define STACKINCREMENT 10
 
typedef char ElemType;
typedef struct
{
 ElemType *base;
 ElemType *top;
 int stackSize;
}sqStack;
 
InitStack(sqStack *s)
{
 s->base = (ElemType *)malloc(STACK_INIT_SIZE * sizeof(ElemType));
 if( !s->base )
  exit(0);
 
 s->top = s->base;
 s->stackSize = STACK_INIT_SIZE;
}
 
Push(sqStack *s, ElemType e)
{
 // 栈满，追加空间，鱼油必须懂！
 if( s->top - s->base >= s->stackSize )
 {
  s->base = (ElemType *)realloc(s->base, (s->stackSize + STACKINCREMENT) * sizeof(ElemType));
  if( !s->base )
   exit(0);
 
  s->top = s->base + s->stackSize;
  s->stackSize = s->stackSize + STACKINCREMENT;
 }
 
 *(s->top) = e;  // 存放数据
 s->top++;
}
 
Pop(sqStack *s, ElemType *e)
{
 if( s->top == s->base )
  return;
 
 *e = *--(s->top); // 将栈顶元素弹出并修改栈顶指针
}
 
int StackLen(sqStack s)
{
 return (s.top - s.base);
}
 
int main()
{
 sqStack s;
 char c, e;
 
 InitStack( &s );
 
 printf("请输入中缀表达式，以#作为结束标志：");
 scanf("%c", &c);
 
 while( c != '#' )
 {
  while( c>='0' && c<='9' )
  {
   printf("%c", c);
   scanf("%c", &c);
   if( c<'0' || c>'9' )
   {
    printf(" ");
   }
  }
 
  if( ')' == c )
  {
   Pop(&s, &e);
   while( '(' != e )
   {
    printf("%c ", e);
    Pop(&s, &e);
   }
  }
  else if( '+'==c || '-'==c )
  {
   if( !StackLen(s) )
   {
    Push(&s, c);
   }
   else
   {
    do
    {
     Pop(&s, &e);
     if( '(' == e )
     {
      Push(&s, e);
     }
     else
     {
      printf("%c ", e);
     }
    }while( StackLen(s) && '('!=e );
    Push(&s, c);
   }
  }
  else if( '*'==c || '/'==c || '('==c )
  {
   Push(&s, c);
  }
  else if( '#'== c )
  {
   break;
  }
  else
  {
   printf("\n出错：输入格式错误！\n");
   return -1;
  }
 
  scanf("%c", &c);
 }
 
 while( StackLen(s) )
 {
  Pop(&s, &e);
  printf("%c ", e);
 }
 
 return 0;
}