Simplify the declarations of the Python code.

codes/python/chapter_array_and_linkedlist/array.py

@@ -70,9 +70,9 @@ def find(nums: list[int], target: int) -> int:
 """Driver Code"""
 if __name__ == "__main__":
     # 初始化数组
-    arr: list[int] = [0] * 5
+    arr = [0] * 5
     print("数组 arr =", arr)
-    nums: list[int] = [1, 3, 2, 5, 4]
+    nums = [1, 3, 2, 5, 4]
     print("数组 nums =", nums)
 
     # 随机访问

codes/python/chapter_array_and_linkedlist/list.py

@@ -7,7 +7,7 @@ Author: Krahets (krahets@163.com)
 """Driver Code"""
 if __name__ == "__main__":
     # 初始化列表
-    arr: list[int] = [1, 3, 2, 5, 4]
+    arr = [1, 3, 2, 5, 4]
     print("列表 arr =", arr)
 
     # 访问元素
@@ -39,17 +39,17 @@ if __name__ == "__main__":
     print("删除索引 3 处的元素，得到 arr =", arr)
 
     # 通过索引遍历列表
-    count: int = 0
+    count = 0
     for i in range(len(arr)):
         count += 1
 
     # 直接遍历列表元素
-    count: int = 0
+    count = 0
     for n in arr:
         count += 1
 
     # 拼接两个列表
-    arr1: list[int] = [6, 8, 7, 10, 9]
+    arr1 = [6, 8, 7, 10, 9]
     arr += arr1
     print("将列表 arr1 拼接到 arr 之后，得到 arr =", arr)
 

codes/python/chapter_backtracking/preorder_traversal_iii_template.py

@@ -35,7 +35,9 @@ def undo_choice(state: list[TreeNode], choice: TreeNode):
     state.pop()
 
 
-def backtrack(state: list[TreeNode], choices: list[TreeNode], res: list[list[TreeNode]]):
+def backtrack(
+    state: list[TreeNode], choices: list[TreeNode], res: list[list[TreeNode]]
+):
     """回溯算法：例题三"""
     # 检查是否为解
     if is_solution(state):

codes/python/chapter_computational_complexity/space_complexity.py

@@ -19,12 +19,12 @@ def function() -> int:
 def constant(n: int) -> None:
     """常数阶"""
     # 常量、变量、对象占用 O(1) 空间
-    a: int = 0
-    nums: list[int] = [0] * 10000
+    a = 0
+    nums = [0] * 10000
     node = ListNode(0)
     # 循环中的变量占用 O(1) 空间
     for _ in range(n):
-        c: int = 0
+        c = 0
     # 循环中的函数占用 O(1) 空间
     for _ in range(n):
         function()
@@ -33,7 +33,7 @@ def constant(n: int) -> None:
 def linear(n: int) -> None:
     """线性阶"""
     # 长度为 n 的列表占用 O(n) 空间
-    nums: list[int] = [0] * n
+    nums = [0] * n
     # 长度为 n 的哈希表占用 O(n) 空间
     mapp = dict[int, str]()
     for i in range(n):
@@ -51,7 +51,7 @@ def linear_recur(n: int) -> None:
 def quadratic(n: int) -> None:
     """平方阶"""
     # 二维列表占用 O(n^2) 空间
-    num_matrix: list[list[int]] = [[0] * n for _ in range(n)]
+    num_matrix = [[0] * n for _ in range(n)]
 
 
 def quadratic_recur(n: int) -> int:
@@ -59,7 +59,7 @@ def quadratic_recur(n: int) -> int:
     if n <= 0:
         return 0
     # 数组 nums 长度为 n, n-1, ..., 2, 1
-    nums: list[int] = [0] * n
+    nums = [0] * n
     return quadratic_recur(n - 1)
 
 

codes/python/chapter_computational_complexity/time_complexity.py

@@ -7,8 +7,8 @@ Author: Krahets (krahets@163.com)
 
 def constant(n: int) -> int:
     """常数阶"""
-    count: int = 0
-    size: int = 100000
+    count = 0
+    size = 100000
     for _ in range(size):
         count += 1
     return count
@@ -16,7 +16,7 @@ def constant(n: int) -> int:
 
 def linear(n: int) -> int:
     """线性阶"""
-    count: int = 0
+    count = 0
     for _ in range(n):
         count += 1
     return count
@@ -24,7 +24,7 @@ def linear(n: int) -> int:
 
 def array_traversal(nums: list[int]) -> int:
     """线性阶（遍历数组）"""
-    count: int = 0
+    count = 0
     # 循环次数与数组长度成正比
     for num in nums:
         count += 1
@@ -33,7 +33,7 @@ def array_traversal(nums: list[int]) -> int:
 
 def quadratic(n: int) -> int:
     """平方阶"""
-    count: int = 0
+    count = 0
     # 循环次数与数组长度成平方关系
     for i in range(n):
         for j in range(n):
@@ -43,7 +43,7 @@ def quadratic(n: int) -> int:
 
 def bubble_sort(nums: list[int]) -> int:
     """平方阶（冒泡排序）"""
-    count: int = 0  # 计数器
+    count = 0  # 计数器
     # 外循环：待排序元素数量为 n-1, n-2, ..., 1
     for i in range(len(nums) - 1, 0, -1):
         # 内循环：冒泡操作
@@ -59,8 +59,8 @@ def bubble_sort(nums: list[int]) -> int:
 
 def exponential(n: int) -> int:
     """指数阶（循环实现）"""
-    count: int = 0
-    base: int = 1
+    count = 0
+    base = 1
     # cell 每轮一分为二，形成数列 1, 2, 4, 8, ..., 2^(n-1)
     for _ in range(n):
         for _ in range(base):
@@ -79,7 +79,7 @@ def exp_recur(n: int) -> int:
 
 def logarithmic(n: float) -> int:
     """对数阶（循环实现）"""
-    count: int = 0
+    count = 0
     while n > 1:
         n = n / 2
         count += 1
@@ -107,7 +107,7 @@ def factorial_recur(n: int) -> int:
     """阶乘阶（递归实现）"""
     if n == 0:
         return 1
-    count: int = 0
+    count = 0
     # 从 1 个分裂出 n 个
     for _ in range(n):
         count += factorial_recur(n - 1)
@@ -130,7 +130,7 @@ if __name__ == "__main__":
 
     count: int = quadratic(n)
     print("平方阶的计算操作数量 =", count)
-    nums: list[int] = [i for i in range(n, 0, -1)]  # [n,n-1,...,2,1]
+    nums = [i for i in range(n, 0, -1)]  # [n, n-1, ..., 2, 1]
     count: int = bubble_sort(nums)
     print("平方阶（冒泡排序）的计算操作数量 =", count)
 

codes/python/chapter_computational_complexity/worst_best_time_complexity.py

@@ -10,7 +10,7 @@ import random
 def random_numbers(n: int) -> list[int]:
     """生成一个数组，元素为: 1, 2, ..., n ，顺序被打乱"""
     # 生成数组 nums =: 1, 2, 3, ..., n
-    nums: list[int] = [i for i in range(1, n + 1)]
+    nums = [i for i in range(1, n + 1)]
     # 随机打乱数组元素
     random.shuffle(nums)
     return nums
@@ -29,7 +29,7 @@ def find_one(nums: list[int]) -> int:
 """Driver Code"""
 if __name__ == "__main__":
     for i in range(10):
-        n: int = 100
+        n = 100
         nums: list[int] = random_numbers(n)
         index: int = find_one(nums)
         print("\n数组 [ 1, 2, ..., n ] 被打乱后 =", nums)

codes/python/chapter_graph/graph_adjacency_matrix.py

@@ -88,8 +88,8 @@ class GraphAdjMat:
 if __name__ == "__main__":
     # 初始化无向图
     # 请注意，edges 元素代表顶点索引，即对应 vertices 元素索引
-    vertices: list[int] = [1, 3, 2, 5, 4]
-    edges: list[list[int]] = [[0, 1], [0, 3], [1, 2], [2, 3], [2, 4], [3, 4]]
+    vertices = [1, 3, 2, 5, 4]
+    edges = [[0, 1], [0, 3], [1, 2], [2, 3], [2, 4], [3, 4]]
     graph = GraphAdjMat(vertices, edges)
     print("\n初始化后，图为")
     graph.print()

codes/python/chapter_hashing/array_hash_map.py

@@ -23,7 +23,7 @@ class ArrayHashMap:
 
     def hash_func(self, key: int) -> int:
         """哈希函数"""
-        index: int = key % 100
+        index = key % 100
         return index
 
     def get(self, key: int) -> str:
@@ -56,7 +56,7 @@ class ArrayHashMap:
 
     def key_set(self) -> list[int]:
         """获取所有键"""
-        result: list[int] = []
+        result = []
         for pair in self.buckets:
             if pair is not None:
                 result.append(pair.key)
@@ -64,7 +64,7 @@ class ArrayHashMap:
 
     def value_set(self) -> list[str]:
         """获取所有值"""
-        result: list[str] = []
+        result = []
         for pair in self.buckets:
             if pair is not None:
                 result.append(pair.val)

codes/python/chapter_heap/heap.py

@@ -64,7 +64,7 @@ if __name__ == "__main__":
 
     # 输入列表并建堆
     # 时间复杂度为 O(n) ，而非 O(nlogn)
-    min_heap: list[int] = [1, 3, 2, 5, 4]
+    min_heap = [1, 3, 2, 5, 4]
     heapq.heapify(min_heap)
     print("\n输入列表并建立小顶堆后")
     print_heap(min_heap)

codes/python/chapter_searching/binary_search.py

@@ -40,8 +40,8 @@ def binary_search_lcro(nums: list[int], target: int) -> int:
 
 """Driver Code"""
 if __name__ == "__main__":
-    target: int = 6
-    nums: list[int] = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
+    target = 6
+    nums = [1, 3, 6, 8, 12, 15, 23, 26, 31, 35]
 
     # 二分查找（双闭区间）
     index: int = binary_search(nums, target)

codes/python/chapter_searching/binary_search_edge.py

@@ -41,8 +41,8 @@ def binary_search_right_edge(nums: list[int], target: int) -> int:
 
 """Driver Code"""
 if __name__ == "__main__":
-    target: int = 6
-    nums: list[int] = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15]
+    target = 6
+    nums = [1, 3, 6, 6, 6, 6, 6, 10, 12, 15]
 
     # 二分查找最左一个元素
     index_left = binary_search_left_edge(nums, target)

codes/python/chapter_searching/hashing_search.py

@@ -28,10 +28,10 @@ def hashing_search_linkedlist(
 
 """Driver Code"""
 if __name__ == "__main__":
-    target: int = 3
+    target = 3
 
     # 哈希查找（数组）
-    nums: list[int] = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8]
+    nums = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8]
     # 初始化哈希表
     map0 = dict[int, int]()
     for i in range(len(nums)):

codes/python/chapter_searching/linear_search.py

@@ -31,10 +31,10 @@ def linear_search_linkedlist(head: ListNode, target: int) -> ListNode | None:
 
 """Driver Code"""
 if __name__ == "__main__":
-    target: int = 3
+    target = 3
 
     # 在数组中执行线性查找
-    nums: list[int] = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8]
+    nums = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8]
     index: int = linear_search_array(nums, target)
     print("目标元素 3 的索引 =", index)
 

codes/python/chapter_sorting/bubble_sort.py

@@ -7,7 +7,7 @@ Author: timi (xisunyy@163.com)
 
 def bubble_sort(nums: list[int]) -> None:
     """冒泡排序"""
-    n: int = len(nums)
+    n = len(nums)
     # 外循环：待排序元素数量为 n-1, n-2, ..., 1
     for i in range(n - 1, 0, -1):
         # 内循环：冒泡操作
@@ -19,10 +19,10 @@ def bubble_sort(nums: list[int]) -> None:
 
 def bubble_sort_with_flag(nums: list[int]) -> None:
     """冒泡排序（标志优化）"""
-    n: int = len(nums)
+    n = len(nums)
     # 外循环：待排序元素数量为 n-1, n-2, ..., 1
     for i in range(n - 1, 0, -1):
-        flag: bool = False  # 初始化标志位
+        flag = False  # 初始化标志位
         # 内循环：冒泡操作
         for j in range(i):
             if nums[j] > nums[j + 1]:
@@ -35,10 +35,10 @@ def bubble_sort_with_flag(nums: list[int]) -> None:
 
 """Driver Code"""
 if __name__ == "__main__":
-    nums: list[int] = [4, 1, 3, 1, 5, 2]
+    nums = [4, 1, 3, 1, 5, 2]
     bubble_sort(nums)
     print("排序后数组 nums =", nums)
 
-    nums1: list[int] = [4, 1, 3, 1, 5, 2]
+    nums1 = [4, 1, 3, 1, 5, 2]
     bubble_sort_with_flag(nums1)
     print("排序后数组 nums =", nums1)

codes/python/chapter_sorting/insertion_sort.py

@@ -9,8 +9,8 @@ def insertion_sort(nums: list[int]) -> None:
     """插入排序"""
     # 外循环：base = nums[1], nums[2], ..., nums[n-1]
     for i in range(1, len(nums)):
-        base: int = nums[i]
-        j: int = i - 1
+        base = nums[i]
+        j = i - 1
         # 内循环：将 base 插入到左边的正确位置
         while j >= 0 and nums[j] > base:
             nums[j + 1] = nums[j]  # 1. 将 nums[j] 向右移动一位
@@ -20,6 +20,6 @@ def insertion_sort(nums: list[int]) -> None:
 
 """Driver Code"""
 if __name__ == "__main__":
-    nums: list[int] = [4, 1, 3, 1, 5, 2]
+    nums = [4, 1, 3, 1, 5, 2]
     insertion_sort(nums)
     print("排序后数组 nums =", nums)

codes/python/chapter_sorting/merge_sort.py

@@ -10,16 +10,16 @@ def merge(nums: list[int], left: int, mid: int, right: int) -> None:
     # 左子数组区间 [left, mid]
     # 右子数组区间 [mid + 1, right]
     # 初始化辅助数组
-    tmp: list[int] = list(nums[left : right + 1])
+    tmp = list(nums[left : right + 1])
     # 左子数组的起始索引和结束索引
-    left_start: int = 0
-    left_end: int = mid - left
+    left_start = 0
+    left_end = mid - left
     # 右子数组的起始索引和结束索引
-    right_start: int = mid + 1 - left
-    right_end: int = right - left
+    right_start = mid + 1 - left
+    right_end = right - left
     # i, j 分别指向左子数组、右子数组的首元素
-    i: int = left_start
-    j: int = right_start
+    i = left_start
+    j = right_start
     # 通过覆盖原数组 nums 来合并左子数组和右子数组
     for k in range(left, right + 1):
         # 若“左子数组已全部合并完”，则选取右子数组元素，并且 j++
@@ -42,7 +42,7 @@ def merge_sort(nums: list[int], left: int, right: int) -> None:
     if left >= right:
         return  # 当子数组长度为 1 时终止递归
     # 划分阶段
-    mid: int = (left + right) // 2  # 计算中点
+    mid = (left + right) // 2  # 计算中点
     merge_sort(nums, left, mid)  # 递归左子数组
     merge_sort(nums, mid + 1, right)  # 递归右子数组
     # 合并阶段
@@ -51,6 +51,6 @@ def merge_sort(nums: list[int], left: int, right: int) -> None:
 
 """Driver Code"""
 if __name__ == "__main__":
-    nums: list[int] = [7, 3, 2, 6, 0, 1, 5, 4]
+    nums = [7, 3, 2, 6, 0, 1, 5, 4]
     merge_sort(nums, 0, len(nums) - 1)
     print("归并排序完成后 nums =", nums)

codes/python/chapter_sorting/quick_sort.py

@@ -29,7 +29,7 @@ class QuickSort:
         if left >= right:
             return
         # 哨兵划分
-        pivot: int = self.partition(nums, left, right)
+        pivot = self.partition(nums, left, right)
         # 递归左子数组、右子数组
         self.quick_sort(nums, left, pivot - 1)
         self.quick_sort(nums, pivot + 1, right)
@@ -51,7 +51,7 @@ class QuickSortMedian:
     def partition(self, nums: list[int], left: int, right: int) -> int:
         """哨兵划分（三数取中值）"""
         # 以 nums[left] 作为基准数
-        med: int = self.median_three(nums, left, (left + right) // 2, right)
+        med = self.median_three(nums, left, (left + right) // 2, right)
         # 将中位数交换至数组最左端
         nums[left], nums[med] = nums[med], nums[left]
         # 以 nums[left] 作为基准数
@@ -73,7 +73,7 @@ class QuickSortMedian:
         if left >= right:
             return
         # 哨兵划分
-        pivot: int = self.partition(nums, left, right)
+        pivot = self.partition(nums, left, right)
         # 递归左子数组、右子数组
         self.quick_sort(nums, left, pivot - 1)
         self.quick_sort(nums, pivot + 1, right)
@@ -102,7 +102,7 @@ class QuickSortTailCall:
         # 子数组长度为 1 时终止
         while left < right:
             # 哨兵划分操作
-            pivot: int = self.partition(nums, left, right)
+            pivot = self.partition(nums, left, right)
             # 对两个子数组中较短的那个执行快排
             if pivot - left < right - pivot:
                 self.quick_sort(nums, left, pivot - 1)  # 递归排序左子数组
@@ -115,16 +115,16 @@ class QuickSortTailCall:
 """Driver Code"""
 if __name__ == "__main__":
     # 快速排序
-    nums: list[int] = [2, 4, 1, 0, 3, 5]
+    nums = [2, 4, 1, 0, 3, 5]
     QuickSort().quick_sort(nums, 0, len(nums) - 1)
     print("快速排序完成后 nums =", nums)
 
     # 快速排序（中位基准数优化）
-    nums1: list[int] = [2, 4, 1, 0, 3, 5]
+    nums1 = [2, 4, 1, 0, 3, 5]
     QuickSortMedian().quick_sort(nums1, 0, len(nums1) - 1)
     print("快速排序（中位基准数优化）完成后 nums =", nums1)
 
     # 快速排序（尾递归优化）
-    nums2: list[int] = [2, 4, 1, 0, 3, 5]
+    nums2= [2, 4, 1, 0, 3, 5]
     QuickSortTailCall().quick_sort(nums2, 0, len(nums2) - 1)
     print("快速排序（尾递归优化）完成后 nums =", nums2)

codes/python/chapter_stack_and_queue/array_queue.py

@@ -53,7 +53,7 @@ class ArrayQueue:
 
     def to_list(self) -> list[int]:
         """返回列表用于打印"""
-        res: list[int] = [0] * self.size()
+        res = [0] * self.size()
         j: int = self.__front
         for i in range(self.size()):
             res[i] = self.__nums[(j % self.capacity())]

codes/python/chapter_stack_and_queue/linkedlist_deque.py

@@ -104,8 +104,8 @@ class LinkedListDeque:
 
     def to_array(self) -> list[int]:
         """返回数组用于打印"""
-        node: ListNode | None = self.front
-        res: list[int] = [0] * self.size()
+        node = self.front
+        res = [0] * self.size()
         for i in range(self.size()):
             res[i] = node.val
             node = node.next

codes/python/chapter_stack_and_queue/linkedlist_stack.py

@@ -49,7 +49,7 @@ class LinkedListStack:
 
     def to_list(self) -> list[int]:
         """转化为列表用于打印"""
-        arr: list[int] = []
+        arr = []
         node = self.__peek
         while node:
             arr.append(node.val)

codes/python/chapter_tree/binary_search_tree.py

@@ -26,7 +26,7 @@ class BinarySearchTree:
             return None
 
         # 将数组中间节点作为根节点
-        mid: int = (start_index + end_index) // 2
+        mid = (start_index + end_index) // 2
         root = TreeNode(nums[mid])
         # 递归建立左子树和右子树
         root.left = self.build_tree(

codes/python/chapter_tree/binary_tree_bfs.py

@@ -17,7 +17,7 @@ def level_order(root: TreeNode | None) -> list[int]:
     queue: deque[TreeNode] = deque()
     queue.append(root)
     # 初始化一个列表，用于保存遍历序列
-    res: list[int] = []
+    res = []
     while queue:
         node: TreeNode = queue.popleft()  # 队列出队
         res.append(node.val)  # 保存节点值

codes/python/modules/binary_tree.py

@@ -22,7 +22,7 @@ def list_to_tree(arr: list[int]) -> TreeNode | None:
     if not arr:
         return None
 
-    i: int = 0
+    i = 0
     root = TreeNode(arr[0])
     queue: deque[TreeNode] = deque([root])
     while queue:

codes/python/modules/print_util.py

@@ -10,10 +10,9 @@ from .linked_list import ListNode, linked_list_to_list
 
 def print_matrix(mat: list[list[int]]) -> None:
     """Print a matrix"""
-    s: list[str] = []
+    s = []
     for arr in mat:
         s.append("  " + str(arr))
-
     print("[\n" + ",\n".join(s) + "\n]")
 
 
@@ -47,7 +46,7 @@ def print_tree(
     if root is None:
         return
 
-    prev_str: str = "    "
+    prev_str = "    "
     trunk = Trunk(prev, prev_str)
     print_tree(root.right, trunk, True)
 

docs/chapter_array_and_linkedlist/list.md

@@ -430,12 +430,12 @@
 
     ```python title="list.py"
     # 通过索引遍历列表
-    count: int = 0
+    count = 0
     for i in range(len(list)):
         count += 1
 
     # 直接遍历列表元素
-    count: int = 0
+    count = 0
     for n in list:
         count += 1
     ```

docs/chapter_computational_complexity/space_complexity.md

@@ -87,10 +87,10 @@
         return 0
 
     def algorithm(n) -> int:  # 输入数据
-        A: int = 0            # 暂存数据（常量，一般用大写字母表示）
-        b: int = 0            # 暂存数据（变量）
+        A = 0                 # 暂存数据（常量，一般用大写字母表示）
+        b = 0                 # 暂存数据（变量）
         node = Node(0)        # 暂存数据（对象）
-        c: int = function()   # 栈帧空间（调用函数）
+        c = function()        # 栈帧空间（调用函数）
         return A + b + c      # 输出数据
     ```
 
@@ -293,10 +293,10 @@
 
     ```python title=""
     def algorithm(n: int) -> None:
-        a: int = 0                     # O(1)
-        b: List[int] = [0] * 10000     # O(1)
+        a = 0                     # O(1)
+        b = [0] * 10000     # O(1)
         if n > 10:
-            nums: List[int] = [0] * n  # O(n)
+            nums = [0] * n  # O(n)
     ```
 
 === "Go"

docs/chapter_computational_complexity/time_complexity.md

@@ -415,7 +415,7 @@ $$
 
     ```python title=""
     def algorithm(n: int) -> None:
-        a: int = 1  # +1
+        a = 1      # +1
         a = a + 1  # +1
         a = a * 2  # +1
         # 循环 n 次
@@ -604,8 +604,8 @@ $$
 
     ```python title=""
     def algorithm(n: int) -> None:
-        a: int = 1  # +0（技巧 1）
-        a = a + n   # +0（技巧 1）
+        a = 1      # +0（技巧 1）
+        a = a + n  # +0（技巧 1）
         # +n（技巧 2）
         for i in range(5 * n + 1):
             print(0)
@@ -619,7 +619,7 @@ $$
 
     ```go title=""
     func algorithm(n int) {
-        a := 1      // +0（技巧 1）
+        a := 1     // +0（技巧 1）
         a = a + n  // +0（技巧 1）
         // +n（技巧 2）
         for i := 0; i < 5 * n + 1; i++ {