題目
用兩個棧實現一個隊列。隊列的聲明如下,請實現它的兩個函數 appendTail 和 deleteHead ,分別完成在隊列尾部插入整數和在隊列頭部刪除整數的功能。(若隊列中沒有元素,deleteHead 操作返回 -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
鏈接:https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof
解題記錄
- 一個棧中存放append的數據
- 另一個棧中存放將要pop出顛倒順序後的數據
import java.util.Deque;
import java.util.LinkedList;
/**
* @author ffzs
* @describe
* @date 2020/6/30
*/
public class CQueue {
Deque<Integer> s1;
Deque<Integer> s2;
public CQueue() {
s1 = new LinkedList<>();
s2 = new LinkedList<>();
}
public void appendTail(int value) {
s1.push(value);
}
public int deleteHead() {
if (!s2.isEmpty()) return s2.pop();
while (!s1.isEmpty()) s2.push(s1.pop());
if (!s2.isEmpty()) return s2.pop();
else return -1;
}
}