2stacksinArray.cpp

class TwoStack{
    int *arr;
    int top1;
    int top2;
    int size;
public:
       
       //Initialize TwoStack.
       TwoStack(int s){
        this -> size = s;
        top1 = -1;
        top2 = s;
       }

       //push in stack 1
       void push1(int num){
        //atleast a empty space present
        if(top2 - top1 > 1){
            top1++;
            arr[top1] = num;
        }
        return -1;
       }

       //push in stack 2
       void push2(int num){
        if(top2 - top1 > 1){
            top2--;
        }
        return -1;
       }

       //pop from stack1 and return popped element
       int pop1(){
        if(top1 >= 0){
            int ans = arr[top1];
            top1--;
            return ans;
        }
        return -1;
       }

       //pop from stack 2 and return popped element
       int pop2() {
        if(top2 < size){
            int ans = arr[top2];
            top2++;
            return ans;
        }
        else{
            return -1;
        }
       }
};