From 2f2e349247ef387b88b334624386574ade332ee5 Mon Sep 17 00:00:00 2001
From: pppig <44393853+pppigg@users.noreply.github.com>
Date: Mon, 17 May 2021 22:29:29 +0800
Subject: [PATCH 1/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200509.=E6=96=90?=
 =?UTF-8?q?=E6=B3=A2=E9=82=A3=E5=A5=91=E6=95=B0=20Python3=E7=89=88?=
 =?UTF-8?q?=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0509.斐波那契数.md | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/problems/0509.斐波那契数.md b/problems/0509.斐波那契数.md
index 8be11312..112c96f9 100644
--- a/problems/0509.斐波那契数.md
+++ b/problems/0509.斐波那契数.md
@@ -187,7 +187,24 @@ class Solution {
 ```
 
 Python：
+```python3
+class Solution:
+    def fib(self, n: int) -> int:
+        if n < 2:
+            return n
+        a, b, c = 0, 1, 0
+        for i in range(1, n):
+            c = a + b
+            a, b = b, c
+        return c
 
+# 递归实现
+class Solution:
+    def fib(self, n: int) -> int:
+        if n < 2:
+            return n
+        return self.fib(n - 1) + self.fib(n - 2)
+```
 
 Go：
 

From 632ec4bdd4af1ae7fdb9692b9d5fb315a43d5e8f Mon Sep 17 00:00:00 2001
From: pppig <44393853+pppigg@users.noreply.github.com>
Date: Tue, 18 May 2021 10:21:30 +0800
Subject: [PATCH 2/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=200707.=E8=AE=BE?=
 =?UTF-8?q?=E8=AE=A1=E9=93=BE=E8=A1=A8=20Python3=E7=89=88=E6=9C=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0707.设计链表.md | 158 ++++++++++++++++++++++++++++++++++
 1 file changed, 158 insertions(+)

diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md
index 93133b55..86cf623b 100644
--- a/problems/0707.设计链表.md
+++ b/problems/0707.设计链表.md
@@ -231,8 +231,166 @@ class MyLinkedList {
 ```
 
 Python：
+```python3
+# 单链表
+class Node:
+    
+    def __init__(self, val):
+        self.val = val
+        self.next = None
 
 
+class MyLinkedList:
+
+    def __init__(self):
+        self._head = Node(0)  # 虚拟头部节点
+        self._count = 0  # 添加的节点数
+
+    def get(self, index: int) -> int:
+        """
+        Get the value of the index-th node in the linked list. If the index is invalid, return -1.
+        """
+        if 0 <= index < self._count:
+            node = self._head
+            for _ in range(index + 1):
+                node = node.next
+            return node.val
+        else:
+            return -1
+
+    def addAtHead(self, val: int) -> None:
+        """
+        Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
+        """
+        self.addAtIndex(0, val)
+
+    def addAtTail(self, val: int) -> None:
+        """
+        Append a node of value val to the last element of the linked list.
+        """
+        self.addAtIndex(self._count, val)
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        """
+        Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted.
+        """
+        if index < 0:
+            index = 0
+        elif index > self._count:
+            return
+
+        # 计数累加
+        self._count += 1
+
+        add_node = Node(val)
+        prev_node, current_node = None, self._head
+        for _ in range(index + 1):
+            prev_node, current_node = current_node, current_node.next
+        else:
+            prev_node.next, add_node.next = add_node, current_node
+
+    def deleteAtIndex(self, index: int) -> None:
+        """
+        Delete the index-th node in the linked list, if the index is valid.
+        """
+        if 0 <= index < self._count:
+            # 计数-1
+            self._count -= 1
+            prev_node, current_node = None, self._head
+            for _ in range(index + 1):
+                prev_node, current_node = current_node, current_node.next
+            else:
+                prev_node.next, current_node.next = current_node.next, None
+
+
+# 双链表
+# 相对于单链表, Node新增了prev属性
+class Node:
+    
+    def __init__(self, val):
+        self.val = val
+        self.prev = None
+        self.next = None
+
+
+class MyLinkedList:
+
+    def __init__(self):
+        self._head, self._tail = Node(0), Node(0)  # 虚拟节点
+        self._head.next, self._tail.prev = self._tail, self._head
+        self._count = 0  # 添加的节点数
+
+    def _get_node(self, index: int) -> Node:
+        # 当index小于_count//2时, 使用_head查找更快, 反之_tail更快
+        if index >= self._count // 2:
+            # 使用prev往前找
+            node = self._tail
+            for _ in range(self._count - index):
+                node = node.prev
+        else:
+            # 使用next往后找
+            node = self._head   
+            for _ in range(index + 1):
+                node = node.next
+        return node
+
+    def get(self, index: int) -> int:
+        """
+        Get the value of the index-th node in the linked list. If the index is invalid, return -1.
+        """
+        if 0 <= index < self._count:
+            node = self._get_node(index)
+            return node.val
+        else:
+            return -1
+
+    def addAtHead(self, val: int) -> None:
+        """
+        Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
+        """
+        self._update(self._head, self._head.next, val)
+
+    def addAtTail(self, val: int) -> None:
+        """
+        Append a node of value val to the last element of the linked list.
+        """
+        self._update(self._tail.prev, self._tail, val)
+
+    def addAtIndex(self, index: int, val: int) -> None:
+        """
+        Add a node of value val before the index-th node in the linked list. If index equals to the length of linked list, the node will be appended to the end of linked list. If index is greater than the length, the node will not be inserted.
+        """
+        if index < 0:
+            index = 0
+        elif index > self._count:
+            return
+        node = self._get_node(index)
+        self._update(node.prev, node, val)
+
+    def _update(self, prev: Node, next: Node, val: int) -> None:
+        """
+            更新节点
+            :param prev: 相对于更新的前一个节点
+            :param next: 相对于更新的后一个节点
+            :param val:  要添加的节点值
+        """
+        # 计数累加
+        self._count += 1
+        node = Node(val)
+        prev.next, next.prev = node, node
+        node.prev, node.next = prev, next
+
+    def deleteAtIndex(self, index: int) -> None:
+        """
+        Delete the index-th node in the linked list, if the index is valid.
+        """
+        if 0 <= index < self._count:
+            node = self._get_node(index)
+            # 计数-1
+            self._count -= 1
+            node.prev.next, node.next.prev = node.next, node.prev
+```
+
 Go：
 
 

From 6079bfa439e29a20dd00693d41bb54c6fcb64d2c Mon Sep 17 00:00:00 2001
From: pppig <44393853+pppigg@users.noreply.github.com>
Date: Tue, 18 May 2021 14:32:32 +0800
Subject: [PATCH 3/3] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=201047.=E5=88=A0?=
 =?UTF-8?q?=E9=99=A4=E5=AD=97=E7=AC=A6=E4=B8=B2=E4=B8=AD=E7=9A=84=E6=89=80?=
 =?UTF-8?q?=E6=9C=89=E7=9B=B8=E9=82=BB=E9=87=8D=E5=A4=8D=E9=A1=B9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 ...047.删除字符串中的所有相邻重复项.md | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/problems/1047.删除字符串中的所有相邻重复项.md b/problems/1047.删除字符串中的所有相邻重复项.md
index d5a8c4ed..607a4ccf 100644
--- a/problems/1047.删除字符串中的所有相邻重复项.md
+++ b/problems/1047.删除字符串中的所有相邻重复项.md
@@ -146,7 +146,17 @@ class Solution {
 ```
 
 Python：
-
+```python3
+class Solution:
+    def removeDuplicates(self, s: str) -> str:
+        t = list()
+        for i in s:
+            if t and t[-1] == i:
+                t.pop(-1)
+            else:
+                t.append(i)
+        return "".join(t)  # 字符串拼接
+```
 
 Go：