Stack Two Array

20 Jun 2019

// Java program to implement two stacks in a 
// single array 
class TwoStacks 
{ 
	int size; 
	int top1, top2; 
	int arr[]; 

	// Constructor 
	TwoStacks(int n) 
	{ 
		arr = new int[n]; 
		size = n; 
		top1 = -1; 
		top2 = size; 
	} 

	// Method to push an element x to stack1 
	void push1(int x) 
	{ 
		// There is at least one empty space for 
		// new element 
		if (top1 < top2 - 1) 
		{ 
			top1++; 
			arr[top1] = x; 
		} 
		else
		{ 
			System.out.println("Stack Overflow"); 
			System.exit(1); 
		} 
	} 

	// Method to push an element x to stack2 
	void push2(int x) 
	{ 
		// There is at least one empty space for 
		// new element 
		if (top1 < top2 -1) 
		{ 
			top2--; 
			arr[top2] = x; 
		} 
		else
		{ 
			System.out.println("Stack Overflow"); 
			System.exit(1); 
		} 
	} 

	// Method to pop an element from first stack 
	int pop1() 
	{ 
		if (top1 >= 0) 
		{ 
			int x = arr[top1]; 
			top1--; 
			return x; 
		} 
		else
		{ 
			System.out.println("Stack Underflow"); 
			System.exit(1); 
		} 
		return 0; 
	} 

	// Method to pop an element from second stack 
	int pop2() 
	{ 
		if(top2 < size) 
		{ 
			int x =arr[top2]; 
			top2++; 
			return x; 
		} 
		else
		{ 
			System.out.println("Stack Underflow"); 
			System.exit(1); 

		} 
		return 0; 
	} 

	// Driver program to test twoStack class 
	public static void main(String args[]) 
	{ 
		TwoStacks ts = new TwoStacks(5); 
		ts.push1(5); 
		ts.push2(10); 
		ts.push2(15); 
		ts.push1(11); 
		ts.push2(7); 
		System.out.println("Popped element from" + 
				" stack1 is " + ts.pop1()); 
		ts.push2(40); 
		System.out.println("Popped element from" + 
				" stack2 is " + ts.pop2()); 
	} 
}