力扣232. 用栈实现队列

class MyQueue {
public:
    MyQueue() {
        
    }
    
    void push(int x) {
        stack_in.push(x);
    }
    
    int pop() {
        if(stack_out.empty()) {
            while(!stack_in.empty()) {
                stack_out.push(stack_in.top());
                stack_in.pop();
            }
        }
        int res = stack_out.top();
        stack_out.pop();
        return res;
    }
    
    int peek() {
        int res = this->pop();
        stack_out.push(res);
        return res;
    }
    
    bool empty() {
        if(stack_in.empty() && stack_out.empty()) return true;
        else return false;
    }
private:
    stack<int> stack_in;
    stack<int> stack_out;
};

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue* obj = new MyQueue();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->peek();
 * bool param_4 = obj->empty();
 */