用两个栈实现队列
用两个栈实现一个队列。队列的声明如下,请实现它的两个函数 appendTail 和 deleteHead ,
分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素,deleteHead 操作返回 -1 )
示例 1: 输入:
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出:[null,null,3,-1]
示例 2:输入:
["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
[[],[],[5],[2],[],[]]
输出:[null,-1,null,null,5,2]
提示:1 <= values <= 10000 最多会对 appendTail、deleteHead 进行 10000 次调用
链接:https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof
class CQueue{
private Deque<Integer> stack1;
private Deque<Integer> stack2;
public CQueue(){
stack1 = new LinkedList<>();
stack2 = new LinkedList<>();
}
private void appendTail(int value){
stack1.push(value);
}
private int deleteItem(){
if (stack2.isEmpty()){
while (!stack1.isEmpty()){
stack2.push(stack1.pop());
}
}
if (stack2.isEmpty()){
return -1;
}else {
int deleteItem = stack2.pop();
return deleteItem;
}
}
}