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/javascript/chapter_searching/two_sum.js

@@ -7,7 +7,7 @@
 /* 方法一：暴力枚举 */
 function twoSumBruteForce(nums, target) {
     const n = nums.length;
-    // 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 (let i = 0; i < n; i++) {
         for (let j = i + 1; j < n; j++) {
             if (nums[i] + nums[j] === target) {
@@ -20,9 +20,9 @@ function twoSumBruteForce(nums, target) {
 
 /* 方法二：辅助哈希表 */
 function twoSumHashTable(nums, target) {
-    // 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)
     let m = {};
-    // 单层循环，时间复杂度 O(n)
+    // 单层循环，时间复杂度为 O(n)
     for (let i = 0; i < nums.length; i++) {
         if (m[target - nums[i]] !== undefined) {
             return [m[target - nums[i]], i];