twoStacks.py

class twoStacks:
    def __init__(self, n):
        self.size = n
        self.arr = [None]*n
        self.top1 = -1
        self.top2 = self.size

    def push1(self, x):
        if self.top1 < self.top2 -1:
            self.top1 = self.top1 + 1
            self.arr[self.top1] = x
        else:
            print('Stack Overflow')
            exit(1)
    def push2(self, x):
        if self.top1 < self.top2 - 1:
            self.top2 = self.top2 - 1
            self.arr[self.top2] = x

        else:
            print('Stack Overflow')

    def pop1(self):
        if self.top1 >= 0:
            x = self.arr[self.top1]
            self.top1 = self.top1 - 1
            return x
        else:
            print('Stack Underflow')
            exit(1)
            
    def pop2(self):
        if self.top2 < self.size:
            x = self.arr[self.top2]
            self.top2 = self.top2 + 1
            return x
        else:
            print('Stack Underflow')
            exit()

#Driver Class
            
ts = twoStacks(5)
ts.push1(5)
ts.push2(10)
ts.push2(15)
ts.push1(11)
ts.push2(7)
 
print("Popped element from stack1 is " + str(ts.pop1()))
ts.push2(40)
print("Popped element from stack2 is " + str(ts.pop2()))