#include <stdio.h>
#include <stdlib.h>
#define MAXNUM 20
#define elemtype int

typedef struct
{
 elemtype Stack[MAXNUM];
 int  LeftTop;
 int RightTop;
}qstype;

void InitiateQStack(qstype *s)//初始化
{
 s->LeftTop=-1;
 s->RightTop=MAXNUM;     
}

int PushQStack(qstype *s,char WhichStack,elemtype x)//进栈
{
 if(s->LeftTop>=s->RightTop-1)
 {
  printf("堆栈已满\n");                             
  return 0;
 }
 if(WhichStack!='L'&&WhichStack!='R')
 {
  printf("参数错误\n");
  return 0;                                    
 }
 if(WhichStack=='L') s->Stack[++s->LeftTop]==x;
 else
 s->Stack[--(s->RightTop)]==x;
 return 1;
}

elemtype PopQStack(qstype *s,char WhichStack)//出栈
{
 if(WhichStack!='L'&&WhichStack!='R')
 {
  printf("参数错误\n");
  return 0;                                    
 }
 if(WhichStack=='L')
 {
  if(s->LeftTop<0)
  {
   printf("左栈已空\n");
   return 0;               
  }         
  return s->Stack[(s->LeftTop)--];
 }
 if(WhichStack=='R')
 {
  if(s->RightTop>MAXNUM)
  {
   printf("右栈已空\n");
   return 0;               
  }         
  return s->Stack[(s->RightTop)++];         
 }                  
}

int main()
{
 char WhichStack;
 qstype *ss=(qstype *)malloc(sizeof(qstype));
 elemtype x,y;
 InitiateQStack(ss);
 printf("请选择插入左表还是右表: 'L'or 'R':\n");
 scanf("%c",&WhichStack);
 while(scanf("%d",&x)!=EOF)
 {
  scanf("%d",&x);
  PushQStack(ss,WhichStack,x);   
 }                       
 printf("请选择出栈的表：'L' or 'R':\n");
 scanf("%c",&WhichStack);
 while(PopQStack(ss,WhichStack))
 {
  y=PopQStack(ss,WhichStack);
  printf("%d\n",y);                                
 }
 getchar();getchar();
 return 0;
}


结果运行错误  怎么回事~~~~~~~