feat: added header files to solutions to help CI

 * Updated the leetcode Readme.md file

Author: nageshnnazare

leetcode/README.md

@@ -24,7 +24,7 @@ All LeetCode problems can be found [**here**](https://leetcode.com/problemset/al
 If you have a solution to any of these problems (which are not being **repeated**, that's great! Here are the steps:
 
 1. Add a new file in `leetcode/src` with the number of the problem.
-    - For example: if the problem's number is 98, the filename should be `98.cpp`.
+   - For example: if the problem's number is 98, the filename should be `98.cpp`.
 2. Provide a small description of the solution at the top of the file. A function should go below that. For example:
 
 ```c
@@ -37,7 +37,7 @@ If you have a solution to any of these problems (which are not being **repeated*
 
 3. Do not provide a `main` function. Use the required standalone functions instead.
 4. Doxygen documentation isn't used in LeetCode solutions. Simple/small documentation or comments should be fine.
-5. Don't include libraries/headers such as `iostream`. Your file should be the solution to the problem only.
+5. Please include dependency libraries/headers such as `<iostream>`, `<vector>` along with the `Solution` class to the problem. This will help the CI to succeed without the dependency errors.
 
 > **Note**
 > There was a requirement to update the `leetcode/DIRECTORY.md` file with details of the solved problem. It's not required anymore. The information about the problem is fetched automatically throughout the LeetCode API.
@@ -66,4 +66,4 @@ git push origin solution/your-solution-name:solution/your-solution-name
 
 4. You're done now! You just have to make a [**pull request**](https://github.com/TheAlgorithms/C-Plus-Plus/compare). 🎉
 
-If you need any help, don't hesitate to ask and join our [**Discord server**](https://the-algorithms.com/discord)! 🙂
+If you need any help, don't hesitate to ask and join our [**Discord server**](https://the-algorithms.com/discord)! 🙂

leetcode/src/1.cpp

@@ -1,8 +1,11 @@
 /*
-* Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
-* You may assume that each input would have exactly one solution, and you may not use the same element twice.
-*/
+ * Given an array of integers nums and an integer target, return indices of the
+ * two numbers such that they add up to target.
+ * You may assume that each input would have exactly one solution, and you may not use the same element twice.
+ */
 
+#include <vector>
+#include <unordered_map>
 class Solution {
 public:
     std::vector<int> twoSum(std::vector<int>& nums, int target) {

leetcode/src/2.cpp

@@ -1,18 +1,19 @@
 /* You are given two non - empty linked lists representing two non - negative integers.
-* The digits are stored in reverse order, and each of their nodes contains a single digit.
-* Add the two numbersand return the sum as a linked list.
-*/
+ * The digits are stored in reverse order, and each of their nodes contains a single digit.
+ * Add the two numbersand return the sum as a linked list.
+ */
 
 /*
  * Definition for singly-linked list.
- * struct ListNode {
- *     int val;
- *     ListNode *next;
- *     ListNode() : val(0), next(nullptr) {}
- *     ListNode(int x) : val(x), next(nullptr) {}
- *     ListNode(int x, ListNode *next) : val(x), next(next) {}
- * };
  */
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode() : val(0), next(nullptr) {}
+    ListNode(int x) : val(x), next(nullptr) {}
+    ListNode(int x, ListNode *next) : val(x), next(next) {}
+};
+
 class Solution {
 public:
     ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {