共享栈

共享栈，利用栈的动态性使栈空间能够互相补充，存储空间能够得到有效利用
  1 #include <iostream>
  2 using namespace std;
  3 #define stacksize 20
  4 typedef struct 
  5 {    
  6     int stack[stacksize];
  7     int top[2];    
  8 }seqstack;
  9 void initstack(seqstack *s)
 10 {
 11     s->top[0]=-1;
 12     s->top[1]=stacksize;
 13 }
 14 int isempty(seqstack *s)
 15 {
 16     if(s->top[0]==-1&&s->top[1]==stacksize)
 17         return 1;
 18     return 0;
 19 }
 20 int pushstack(seqstack *s,int num,bool flag)
 21 {
 22     if(s->top[0]==s->top[1])
 23     {
 24         cout<<"栈满"<<endl;
 25         return 0;
 26     }
 27     switch(flag)
 28     {
 29         case 0:            /*入左栈*/
 30             s->top[0]++;
 31             s->stack[s->top[0]]=num;
 32             break;
 33         case 1:
 34             s->top[1]--;
 35             s->stack[s->top[1]]=num;
 36             break;
 37         default:
 38             break;
 39     }
 40     return 0;
 41 }
 42 int popstack(seqstack *s,bool flag)
 43 {
 44     switch(flag)
 45     {
 46         case 0:
 47             if(s->top[0]==-1)
 48             {
 49                 cout<<"空栈";
 50                 return 0;
 51             }
 52             else
 53                 s->top[0]--;
 54             break;
 55         case 1:
 56             if(s->top[1]==stacksize)
 57             {
 58                 cout<<"空栈";
 59                 return 0;
 60             }
 61             else
 62                 s->top[1]++;        
 63         default:
 64             break;
 65     }
 66 }
 67 int getstack(seqstack *s,bool flag)
 68 {
 69     switch(flag)
 70     {
 71         case 0:
 72             if(s->top[0]==-1)
 73             {
 74                 cout<<"空栈";
 75                 return 0;
 76             }
 77             else
 78                 cout<<s->stack[s->top[0]]<<endl;
 79                 break;
 80         case 1:
 81             if(s->top[1]==stacksize)
 82             {
 83                 cout<<"空栈";
 84                 return 0;
 85             }
 86             else
 87                 cout<<s->stack[s->top[1]]<<endl;
 88                 break;    
 89         default:
 90             break;
 91     }
 92 }
 93 int main()
 94 {
 95     seqstack s;
 96     initstack(&s);
 97     pushstack(&s,1,0);
 98     pushstack(&s,2,0);
 99     pushstack(&s,3,0);
100     pushstack(&s,9,1);
101     pushstack(&s,8,1);
102     pushstack(&s,7,1);
103     getstack(&s,1);
104     popstack(&s,1);
105     getstack(&s,1);
106 }