Add figures to replace_linear_by_hashing.md

codes/javascript/chapter_searching/two_sum.js

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+/**
+ * File: two_sum.js
+ * Created Time: 2022-12-15
+ * Author: gyt95 (gytkwan@gmail.com)
+ */
+
+/* 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)
+    for (let i = 0; i < n; i++) {
+        for (let j = i + 1; j < n; j++) {
+            if (nums[i] + nums[j] === target) {
+                return [i, j];
+            }
+        }
+    }
+    return [];
+}
+
+/* 方法二：辅助哈希表 */
+function twoSumHashTable(nums, target) {
+    // 辅助哈希表，空间复杂度 O(n)
+    let m = {};
+    // 单层循环，时间复杂度 O(n)
+    for (let i = 0; i < nums.length; i++) {
+        if (m[nums[i]] !== undefined) {
+            return [m[nums[i]], i];
+        } else {
+            m[target - nums[i]] = i;
+        }
+    }
+    return [];
+}
+
+/* Driver Code */
+// 方法一
+const nums = [2, 7, 11, 15],
+    target = 13;
+
+let res = twoSumBruteForce(nums, target);
+console.log('方法一 res = ', res);
+
+// 方法二
+res = twoSumHashTable(nums, target);
+console.log('方法二 res = ', res);