C++利用两个栈实现队列的方法

#include <iostream>#include <stack>#include <exception>template<class T> class MyQueue { public: void push(const T& num); // 入队列 T pop(); // 出队列 T top(); private: std::stack<T> pushStack; std::stack<T> popStack;};template<typename T>void MyQueue<T>::push(const T& num) { pushStack.push(num);}template<typename T>T MyQueue<T>::pop() { if (pushStack.empty() && popStack.empty()) { // 如果二个栈都为空 throw std::runtime_error("queue is empty"); } else if (popStack.empty()) { // 如果popStack为空,将pushStack全部元素倒popStack while (!pushStack.empty()) { T data = pushStack.top(); // 获取pushStack栈顶元素 pushStack.pop(); // 出栈 popStack.push(data); } } T data = popStack.top(); popStack.pop(); return data;}template<typename T>T MyQueue<T>::top() { if (pushStack.empty() && popStack.empty()) { // 如果二个栈都为空 throw std::runtime_error("queue is empty"); } else if (popStack.empty()) { // 如果popStack为空,将pushStack全部元素倒popStack while (!pushStack.empty()) { T data = pushStack.top(); // 获取pushStack栈顶元素 pushStack.pop(); // 出栈 popStack.push(data); } } else { // 如果popStack不为空的话直接返回popStack栈顶 T data = popStack.top(); return data; }}int main() { MyQueue<int> myQueue1; myQueue1.push(1); myQueue1.push(2); myQueue1.push(3); myQueue1.push(4); std::cout << "current pop is:" << myQueue1.pop() << std::endl; std::cout << "current pop is:" << myQueue1.pop() << std::endl; std::cout << "current pop is:" << myQueue1.pop() << std::endl; std::cout << "current pop is:" << myQueue1.pop() << std::endl; std::cout << "current pop is:" << myQueue1.pop() << std::endl; return 0;}