Implement Stack using Queues

Description:

Implement the following operations of a stack using queues.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• empty() -- Return whether the stack is empty.

Notes:

• You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
• Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
• You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

Solution:

class Stack {
private:
	queue<int> q;

public:
	// Push element x onto stack.
	void push(int x) {
		q.push(x);
		for (int i = 0; i < q.size()-1; ++i) {
			q.push(q.front());
			q.pop();
		}
	}

	// Removes the element on top of the stack.
	void pop() {
		q.pop();
	}

	// Get the top element.
	int top() {
		return q.front();
	}

	// Return whether the stack is empty.
	bool empty() {
		return q.empty();
	}
};