剑指 Offer 09. 用两个栈实现队列C++

class CQueue {
public:
    stack<int>stack1;
    stack<int>stack2;
    CQueue() {
    }
    void appendTail(int value) {
        stack1.push(value);
    }
    int deleteHead() {
     if(stack1.empty())  return -1;
     while(!stack1.empty()){
         stack2.push(stack1.top());
         stack1.pop();
     }
     int res = stack2.top();
     stack2.pop();
     while(!stack2.empty()){
         stack1.push(stack2.top());
         stack2.pop();
     }
     return res;
    }
};