用兩個棧實作隊列
用兩個棧實作一個隊列。隊列的聲明如下,請實作它的兩個函數 appendTail 和 deleteHead ,
分别完成在隊列尾部插入整數和在隊列頭部删除整數的功能。(若隊列中沒有元素,deleteHead 操作傳回 -1 )
示例 1: 輸入:
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
輸出:[null,null,3,-1]
示例 2:輸入:
["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
[[],[],[5],[2],[],[]]
輸出:[null,-1,null,null,5,2]
提示:1 <= values <= 10000 最多會對 appendTail、deleteHead 進行 10000 次調用
連結: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;
}
}
}