力扣：剑指 Offer 09:用两个栈实现队列

LeetCode/src/main/java/leetcode/editor/cn/YongLiangGeZhanShiXianDuiLieLcof.java

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+//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 
+// 
+// Related Topics 栈 设计 
+// 👍 212 👎 0
+
+package leetcode.editor.cn;
+
+import java.util.Stack;
+
+//剑指 Offer 09:用两个栈实现队列
+public class YongLiangGeZhanShiXianDuiLieLcof {
+    public static void main(String[] args) {
+        //测试代码
+//        Solution solution = new YongLiangGeZhanShiXianDuiLieLcof().new Solution();
+    }
+
+    //力扣代码
+    //leetcode submit region begin(Prohibit modification and deletion)
+    class CQueue {
+        Stack<Integer> stack1;
+        Stack<Integer> stack2;
+
+        public CQueue() {
+            stack1 = new Stack<>();
+            stack2 = new Stack<>();
+        }
+
+        public void appendTail(int value) {
+            stack1.push(value);
+        }
+
+        public int deleteHead() {
+            if (stack2.isEmpty()) {
+                while (!stack1.isEmpty()) {
+                    stack2.push(stack1.pop());
+                }
+            }
+            return stack2.isEmpty() ? -1 : stack2.pop();
+        }
+    }
+
+/**
+ * Your CQueue object will be instantiated and called as such:
+ * CQueue obj = new CQueue();
+ * obj.appendTail(value);
+ * int param_2 = obj.deleteHead();
+ */
+//leetcode submit region end(Prohibit modification and deletion)
+
+}

LeetCode/src/main/java/leetcode/editor/cn/YongLiangGeZhanShiXianDuiLieLcof.md

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+<p>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 <code>appendTail</code> 和 <code>deleteHead</code> ，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，<code>deleteHead</code>&nbsp;操作返回 -1 )</p>
+
+<p>&nbsp;</p>
+
+<p><strong>示例 1：</strong></p>
+
+<pre><strong>输入：</strong>
+[&quot;CQueue&quot;,&quot;appendTail&quot;,&quot;deleteHead&quot;,&quot;deleteHead&quot;]
+[[],[3],[],[]]
+<strong>输出：</strong>[null,null,3,-1]
+</pre>
+
+<p><strong>示例 2：</strong></p>
+
+<pre><strong>输入：</strong>
+[&quot;CQueue&quot;,&quot;deleteHead&quot;,&quot;appendTail&quot;,&quot;appendTail&quot;,&quot;deleteHead&quot;,&quot;deleteHead&quot;]
+[[],[],[5],[2],[],[]]
+<strong>输出：</strong>[null,-1,null,null,5,2]
+</pre>
+
+<p><strong>提示：</strong></p>
+
+<ul>
+	<li><code>1 &lt;= values &lt;= 10000</code></li>
+	<li><code>最多会对&nbsp;appendTail、deleteHead 进行&nbsp;10000&nbsp;次调用</code></li>
+</ul>
+<div><div>Related Topics</div><div><li>栈</li><li>设计</li></div></div>\n<div><li>👍 212</li><li>👎 0</li></div>