solve.cpp

#include <stack>
#include <iostream>
using namespace std;
class Queue {
	private:
		stack<int> first;
		stack<int> second;
	public:
		bool empty(void) {
			return first.empty() && second.empty();
		}
		void push(int x) {
			first.push(x);
		}
		int peek(void) {
			if (second.empty()) {
				channel(first, second);
			}
			return second.top();
		}
		void pop(void) {
			if (second.empty()) {
				channel(first, second);
			}
			second.pop();
		}
	private:
		void channel(stack<int> &src, stack<int> &dest) {
			while (!src.empty()) {
				dest.push(src.top());
				src.pop();
			}
		}
};
int main(int argc, char **argv)
{
	Queue queue;
	queue.push(1);
	queue.push(2);
	queue.pop();
	cout << queue.peek() << endl;
	return 0;
}