题目

解题代码

class CQueue {
    Stack<Integer> stackPush ; //压栈
    Stack<Integer> stackPop ; //出栈
    public CQueue() { 
        // 初始化
        stackPush = new Stack<>();
        stackPop = new Stack<>();
    }
    public void appendTail(int value) {
        stackPush.push(value); //入栈
    }
    public int deleteHead() {
        if(stackPop.isEmpty() ) {
            while( !stackPush.isEmpty() ) { 
                //将入栈信息全部压入弹出栈
                stackPop.push(stackPush.pop() );
            }
        }
        return stackPop.isEmpty() ?  -1 : stackPop.pop();
    }
}
/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue obj = new CQueue();
 * obj.appendTail(value);
 * int param_2 = obj.deleteHead();
 */