Implement two stacks in an array

PROBLEM :

Your task is to implement  2 stacks in  one array efficiently .

Input (To be used for Expected Output):

The first line of the input contains an integer 'T' denoting the number of test cases. Then T test cases follow.
First line of each test case contains an integer Q denoting the number of queries .
 A Query Q is of 4 Types
(i)    1 1 x    (a query of this type means  pushing 'x' into the stack 1)
(ii)   1 2      (a query of this type means to pop element from stack1  and print the poped element)
(iii)  2 1 x  (a query of this type means poushing 'x' into the stack 2)
(iv)  2 2     (a query of this type means to pop element from stack2 and print the poped element)

The second line of each test case contains Q queries seperated by space.

Output:
The output for each test case will  be space separated integers having -1 if the stack is empty else the element poped out from the stack.
You are required to complete the 4  methods push1, push2 which takes one argument an integer 'x' to be pushed into the stack one and two  and pop1, pop2 which returns a integer poped out from stack one and two .

Constraints:
1<=T<=100
1<=Q<=100
1<=x<=100

Example:
Input
1
6
1 1 2 1 1 3 2 1 4 1 2 2 2 2 2

Output
3 4 -1

Explanation:

In the first test case for query
1 1 2    the stack1 will be {2}
1 1 3    the stack1 will be {2,3}
2 1 4   the stack2 will be {4}
1 2      the poped element will be 3 from stack1 and stack1 will be {2}
2 2      the poped element will be 4 from stack2 and now stack2 is empty
2 2      the stack2 is now empty hence -1 .


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SIMPLE c++ IMPLEMENTATION :
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/*The structure of the class is
class twoStacks
{
    int *arr;
    int size;
    int top1, top2;
public:
   twoStacks(int n=100){size = n; arr = new int[n]; top1 = -1; top2 = size;}

   void push1(int x);
   void push2(int x);
   int pop1();
   int pop2();
};
*/


/* The method push to push element into the stack 2 */
void twoStacks :: push1(int x)
   {
        if(top1>=top2)
            return ;
        arr[++top1]=x ;
   }
 
/* The method push to push element into the stack 2*/
void twoStacks ::push2(int x)
   {
        if(top1>=top2)
            return ;
        arr[--top2]=x ;
   }
 
/* The method pop to pop element from the stack 1 */
int twoStacks ::pop1()
   {
       if(top1==-1)
            return -1 ;
       else
            return(arr[top1--]) ;

   }

/* The method pop to pop element from the stack 2 */
int twoStacks :: pop2()
   {
        if(top2==size)
            return -1 ;
       else
            return(arr[top2++]) ;
   }

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COMPLETE STACK IMPLEMENTATION IN ARRAY :
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// implementing two stack in a single array

#include<iostream>
using namespace std ;
#include<malloc.h>

typedef struct STACK
{
int top1,top2 ;
int capasity ;
int *array ;
}stack ;

void create_stack(stack **,int );
void push_stack1(stack **,int );
void push_stack2(stack **,int );
int pop_stack1(stack **);
int pop_stack2(stack **);
int isfull_stack(stack *);
int isempty_stack(stack *);
void display_stack1(stack *) ;
void display_stack2(stack *) ;


int main()
{
stack *s ;
int no,choice,i,ele ;

cout<<"\n enter the capacity of the stack " ;
cin>>no ;

create_stack(&s,no) ;

do
{
cout<<"\n 1. push elemet in the first stack  " ;
cout<<"\n 2. push elemet in the second stack  " ;
cout<<"\n 3. pop element from the first stack " ;
cout<<"\n 4. pop element from the second stack " ;
cout<<"\n 5. display first stack " ;
cout<<"\n 6. display second stack " ;
cout<<"\n enter choice" ;
cin>>choice ;
switch(choice)
{
case 1 :cout<<"\n enter no of elemets to push " ;
cin>>no ;
cout<<"\n enter th elemets " ;
for(i=0;i<no;i++)
{
cin>>ele ;
push_stack1(&s,ele) ;
}
break ;
case 2 :cout<<"\n enter no of elemets to push " ;
cin>>no ;
cout<<"\n enter th elemets " ;
for(i=0;i<no;i++)
{
cin>>ele ;
push_stack2(&s,ele) ;
}
break ;
case 3 :ele=pop_stack1(&s) ;
if(ele!=-1)
cout<<"\n elemet poped is = "<<ele ;
break ;
case 4 :ele=pop_stack1(&s) ;
if(ele!=-1)
cout<<"\n elemet poped is = "<<ele ;
break ;
case 5 :display_stack1(s) ;
break ;
case 6 :display_stack2(s) ;
break ;

default : cout<<"\n TRY AGAIN !!!!" ;
}
cout<<"\n enter 1 to continue " ;
cin>>no ;
}while(no==1) ;

return 0 ;
}

void create_stack(stack **s,int no)
{
(*s)=(stack*)malloc(sizeof(stack)) ;
(*s)->top1=-1;
(*s)->top2=no ;
(*s)->capasity=no ;
(*s)->array=(int*)malloc((*s)->capasity*(sizeof(int))) ;
}

void push_stack1(stack **s,int data)
{
if(isfull_stack(*s))
{
cout<<"\n SORRY !!! can't take more input !!! STACK FULLL" ;
return ;
}
(*s)->array[++((*s)->top1)]=data ;
}

void push_stack2(stack **s,int data)
{
if(isfull_stack(*s))
{
cout<<"\n SORRY !!! can't take more input !!! STACK FULLL" ;
return ;
}
(*s)->array[--((*s)->top2)]=data ;
}

int pop_stack1(stack **s)
{
if(isempty_stack(*s))
{
cout<<"\n SORRY !!! stack is empty !! no elemet to POP" ;
return -1 ;
}
return((*s)->array[((*s)->top1)--]) ;
}

int pop_stack2(stack **s)
{
if(isempty_stack(*s))
{
cout<<"\n SORRY !!! stack is empty !! no elemet to POP" ;
return -1 ;
}
return((*s)->array[((*s)->top2)--]) ;
}

void display_stack1(stack *s)
{
if(isempty_stack(s))
{
cout<<"\n SORRY !!! stack is empty !! no elemet to display" ;
return  ;
}
int i ;
for(i=0;i<=s->top1;i++)
cout<<s->array[i]<<" " ;
}

void display_stack2(stack *s)
{
if(isempty_stack(s))
{
cout<<"\n SORRY !!! stack is empty !! no elemet to display" ;
return  ;
}
int i ;
for(i=s->top2;i<s->capasity;i++)
cout<<s->array[i]<<" " ;
}

int isfull_stack(stack *s)
{
if(s->top1+1>=s->top2)
return 1 ;
return 0 ;
}

int isempty_stack(stack *s)
{
if(s->top1==-1&&s->top2==s->capasity)
return 1 ;
return 0 ;
}

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