Add the initial EN translation for C++ code (#1346)

en/codes/cpp/chapter_searching/two_sum.cpp

@@ -0,0 +1,54 @@
+/**
+ * File: two_sum.cpp
+ * Created Time: 2022-11-25
+ * Author: krahets (krahets@163.com)
+ */
+
+#include "../utils/common.hpp"
+
+/* Method one: Brute force enumeration */
+vector<int> twoSumBruteForce(vector<int> &nums, int target) {
+    int size = nums.size();
+    // Two-layer loop, time complexity is 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 {};
+}
+
+/* Method two: Auxiliary hash table */
+vector<int> twoSumHashTable(vector<int> &nums, int target) {
+    int size = nums.size();
+    // Auxiliary hash table, space complexity is O(n)
+    unordered_map<int, int> dic;
+    // Single-layer loop, time complexity is 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 {};
+}
+
+/* Driver Code */
+int main() {
+    // ======= Test Case =======
+    vector<int> nums = {2, 7, 11, 15};
+    int target = 13;
+
+    // ====== Driver Code ======
+    // Method one
+    vector<int> res = twoSumBruteForce(nums, target);
+    cout << "Method one res = ";
+    printVector(res);
+    // Method two
+    res = twoSumHashTable(nums, target);
+    cout << "Method two res = ";
+    printVector(res);
+
+    return 0;
+}