Refactor the articles related to searching algorithm. Add the chapter of binary search. Add the section of searching algorithm revisited. (#464)

codes/cpp/chapter_searching/leetcode_two_sum.cpp

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+/**
+ * File: leetcode_two_sum.cpp
+ * Created Time: 2022-11-25
+ * Author: Krahets (krahets@163.com)
+ */
+
+#include "../include/include.hpp"
+
+/* 方法一：暴力枚举 */
+vector<int> twoSumBruteForce(vector<int> &nums, int target) {
+    int size = nums.size();
+    // 两层循环，时间复杂度 O(n^2)
+    for (int i = 0; i < size - 1; i++) {
+        for (int j = i + 1; j < size; j++) {
+            if (nums[i] + nums[j] == target)
+                return {i, j};
+        }
+    }
+    return {};
+}
+
+/* 方法二：辅助哈希表 */
+vector<int> twoSumHashTable(vector<int> &nums, int target) {
+    int size = nums.size();
+    // 辅助哈希表，空间复杂度 O(n)
+    unordered_map<int, int> dic;
+    // 单层循环，时间复杂度 O(n)
+    for (int i = 0; i < size; i++) {
+        if (dic.find(target - nums[i]) != dic.end()) {
+            return {dic[target - nums[i]], i};
+        }
+        dic.emplace(nums[i], i);
+    }
+    return {};
+}
+
+int main() {
+    // ======= Test Case =======
+    vector<int> nums = {2, 7, 11, 15};
+    int target = 9;
+
+    // ====== Driver Code ======
+    // 方法一
+    vector<int> res = twoSumBruteForce(nums, target);
+    cout << "方法一 res = ";
+    printVector(res);
+    // 方法二
+    res = twoSumHashTable(nums, target);
+    cout << "方法二 res = ";
+    printVector(res);
+
+    return 0;
+}