From d5b378e1421c93d64f86c9752dd34ba39e7bf37c Mon Sep 17 00:00:00 2001 From: LehiChiang <1471277588@qq.com> Date: Wed, 12 May 2021 21:01:25 +0800 Subject: [PATCH 1/2] =?UTF-8?q?=E6=B7=BB=E5=8A=A00111.=E4=BA=8C=E5=8F=89?= =?UTF-8?q?=E6=A0=91=E7=9A=84=E6=9C=80=E5=B0=8F=E6=B7=B1=E5=BA=A6=20Python?= =?UTF-8?q?=E7=89=88=E6=9C=AC=E3=80=82?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0111.二叉树的最小深度.md | 46 ++++++++++++++++++++++- 1 file changed, 44 insertions(+), 2 deletions(-) diff --git a/problems/0111.二叉树的最小深度.md b/problems/0111.二叉树的最小深度.md index 430cd5d6..6c6b4632 100644 --- a/problems/0111.二叉树的最小深度.md +++ b/problems/0111.二叉树的最小深度.md @@ -195,9 +195,51 @@ public: Java： - Python： +递归法： + +```python +class Solution: + def minDepth(self, root: TreeNode) -> int: + if not root: + return 0 + if not root.left and not root.right: + return 1 + + min_depth = 10**9 + if root.left: + min_depth = min(self.minDepth(root.left), min_depth) # 获得左子树的最小高度 + if root.right: + min_depth = min(self.minDepth(root.right), min_depth) # 获得右子树的最小高度 + return min_depth + 1 +``` + +迭代法： + +```python +class Solution: + def minDepth(self, root: TreeNode) -> int: + if not root: + return 0 + que = deque() + que.append(root) + res = 1 + + while que: + for _ in range(len(que)): + node = que.popleft() + # 当左右孩子都为空的时候，说明是最低点的一层了，退出 + if not node.left and not node.right: + return res + if node.left is not None: + que.append(node.left) + if node.right is not None: + que.append(node.right) + res += 1 + return res +``` + Go： @@ -208,4 +250,4 @@ Go： * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ) -
+
\ No newline at end of file From 49eed9c8a3d4f862c5ff75c08c31c0fe54bf2fbf Mon Sep 17 00:00:00 2001 From: LehiChiang <1471277588@qq.com> Date: Wed, 12 May 2021 22:56:39 +0800 Subject: [PATCH 2/2] =?UTF-8?q?=E6=B7=BB=E5=8A=A00225.=E7=94=A8=E9=98=9F?= =?UTF-8?q?=E5=88=97=E5=AE=9E=E7=8E=B0=E6=A0=88/0232.=E7=94=A8=E6=A0=88?= =?UTF-8?q?=E5=AE=9E=E7=8E=B0=E9=98=9F=E5=88=97=20Java=E7=89=88=E6=9C=AC?= =?UTF-8?q?=E3=80=82?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0225.用队列实现栈.md | 53 +++++++++++++++++++++++++- problems/0232.用栈实现队列.md | 59 +++++++++++++++++++++++++++-- 2 files changed, 107 insertions(+), 5 deletions(-) diff --git a/problems/0225.用队列实现栈.md b/problems/0225.用队列实现栈.md index 49b5c62b..4018364a 100644 --- a/problems/0225.用队列实现栈.md +++ b/problems/0225.用队列实现栈.md @@ -154,9 +154,58 @@ public: ## 其他语言版本 - Java： +```java +class MyStack { + + Queue queue1; // 和栈中保持一样元素的队列 + Queue queue2; // 辅助队列 + + /** Initialize your data structure here. */ + public MyStack() { + queue1 = new LinkedList<>(); + queue2 = new LinkedList<>(); + } + + /** Push element x onto stack. */ + public void push(int x) { + queue2.offer(x); // 先放在辅助队列中 + while (!queue1.isEmpty()){ + queue2.offer(queue1.poll()); + } + Queue queueTemp; + queueTemp = queue1; + queue1 = queue2; + queue2 = queueTemp; // 最后交换queue1和queue2，将元素都放到queue1中 + } + + /** Removes the element on top of the stack and returns that element. */ + public int pop() { + return queue1.poll(); // 因为queue1中的元素和栈中的保持一致，所以这个和下面两个的操作只看queue1即可 + } + + /** Get the top element. */ + public int top() { + return queue1.peek(); + } + + /** Returns whether the stack is empty. */ + public boolean empty() { + return queue1.isEmpty(); + } +} + +/** + * Your MyQueue object will be instantiated and called as such: + * MyQueue obj = new MyQueue(); + * obj.push(x); + * int param_2 = obj.pop(); + * int param_3 = obj.peek(); + * boolean param_4 = obj.empty(); + */ +``` + Python： @@ -227,4 +276,4 @@ Go： * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ) -
+
\ No newline at end of file diff --git a/problems/0232.用栈实现队列.md b/problems/0232.用栈实现队列.md index 9907b476..abdc363d 100644 --- a/problems/0232.用栈实现队列.md +++ b/problems/0232.用栈实现队列.md @@ -19,7 +19,7 @@ push(x) -- 将一个元素放入队列的尾部。 pop() -- 从队列首部移除元素。 peek() -- 返回队列首部的元素。 empty() -- 返回队列是否为空。 -  + 示例: @@ -129,9 +129,62 @@ public: ## 其他语言版本 - Java： +```java +class MyQueue { + + Stack stack1; + Stack stack2; + + /** Initialize your data structure here. */ + public MyQueue() { + stack1 = new Stack<>(); // 负责进栈 + stack2 = new Stack<>(); // 负责出栈 + } + + /** Push element x to the back of queue. */ + public void push(int x) { + stack1.push(x); + } + + /** Removes the element from in front of queue and returns that element. */ + public int pop() { + dumpStack1(); + return stack2.pop(); + } + + /** Get the front element. */ + public int peek() { + dumpStack1(); + return stack2.peek(); + } + + /** Returns whether the queue is empty. */ + public boolean empty() { + return stack1.isEmpty() && stack2.isEmpty(); + } + + // 如果stack2为空，那么将stack1中的元素全部放到stack2中 + private void dumpStack1(){ + if (stack2.isEmpty()){ + while (!stack1.isEmpty()){ + stack2.push(stack1.pop()); + } + } + } +} + +/** + * Your MyQueue object will be instantiated and called as such: + * MyQueue obj = new MyQueue(); + * obj.push(x); + * int param_2 = obj.pop(); + * int param_3 = obj.peek(); + * boolean param_4 = obj.empty(); + */ +``` + Python： @@ -145,4 +198,4 @@ Go： * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw) * B站视频：[代码随想录](https://space.bilibili.com/525438321) * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ) -
+
\ No newline at end of file