【2021秋冬】【剑指offer】09. 用两个栈实现队列

java栈的写法

Stack stack = new Stack<>();
stack.isEmpty();
stack.push(1);
stack.pop();
stack.peek(); // 返回栈顶
stack.size();

class CQueue {
    Stack stack1;
    Stack stack2;
    public CQueue() {
        stack1 = new Stack<>();
        stack2 = new Stack<>();

    }
    
    public void appendTail(int value) {
        stack1.push(value);

    }
    
    public int deleteHead() {
        if(!stack2.isEmpty()) return stack2.pop();
        if(stack1.isEmpty()) return -1;
        while(!stack1.isEmpty()){
            stack2.push(stack1.pop());
        }
        return stack2.pop();
    }
}