feat: Revised the book (#978)

* Sync recent changes to the revised Word.

* Revised the preface chapter

* Revised the introduction chapter

* Revised the computation complexity chapter

* Revised the chapter data structure

* Revised the chapter array and linked list

* Revised the chapter stack and queue

* Revised the chapter hashing

* Revised the chapter tree

* Revised the chapter heap

* Revised the chapter graph

* Revised the chapter searching

* Reivised the sorting chapter

* Revised the divide and conquer chapter

* Revised the chapter backtacking

* Revised the DP chapter

* Revised the greedy chapter

* Revised the appendix chapter

* Revised the preface chapter doubly

* Revised the figures

codes/python/chapter_searching/two_sum.py

@@ -7,7 +7,7 @@ Author: Krahets (krahets@163.com)
 
 def two_sum_brute_force(nums: list[int], target: int) -> list[int]:
     """方法一：暴力枚举"""
-    # 两层循环，时间复杂度 O(n^2)
+    # 两层循环，时间复杂度为 O(n^2)
     for i in range(len(nums) - 1):
         for j in range(i + 1, len(nums)):
             if nums[i] + nums[j] == target:
@@ -17,9 +17,9 @@ def two_sum_brute_force(nums: list[int], target: int) -> list[int]:
 
 def two_sum_hash_table(nums: list[int], target: int) -> list[int]:
     """方法二：辅助哈希表"""
-    # 辅助哈希表，空间复杂度 O(n)
+    # 辅助哈希表，空间复杂度为 O(n)
     dic = {}
-    # 单层循环，时间复杂度 O(n)
+    # 单层循环，时间复杂度为 O(n)
     for i in range(len(nums)):
         if target - nums[i] in dic:
             return [dic[target - nums[i]], i]