diff --git a/Easy/best-time-to-buy-and-sell-stock/solution.cpp b/Easy/best-time-to-buy-and-sell-stock/solution.cpp
index f643e3b..c2949ab 100644
--- a/Easy/best-time-to-buy-and-sell-stock/solution.cpp
+++ b/Easy/best-time-to-buy-and-sell-stock/solution.cpp
@@ -1,5 +1,7 @@
+#include <vector>
+
 class Solution {
-  public:
+public:
     int maxProfit(std::vector<int> &prices) {
         int prof = 0;
         for (int i = prices.size() - 1, max = 0; i >= 0; --i) {
diff --git a/Easy/binary-tree-postorder-traversal/solution.cpp b/Easy/binary-tree-postorder-traversal/solution.cpp
index 3804ac9..90f0217 100644
--- a/Easy/binary-tree-postorder-traversal/solution.cpp
+++ b/Easy/binary-tree-postorder-traversal/solution.cpp
@@ -11,7 +11,7 @@ struct TreeNode {
 };
 
 class Solution {
-  private:
+private:
     void traverse(std::vector<int> &list, TreeNode *root) {
         if (root == nullptr) {
             return;
@@ -22,7 +22,7 @@ class Solution {
         }
     }
 
-  public:
+public:
     std::vector<int> postorderTraversal(TreeNode *root) {
         std::vector<int> list;
         traverse(list, root);
diff --git a/Easy/binary-tree-preorder-traversal/solution.cpp b/Easy/binary-tree-preorder-traversal/solution.cpp
index eaa4bf2..e33886d 100644
--- a/Easy/binary-tree-preorder-traversal/solution.cpp
+++ b/Easy/binary-tree-preorder-traversal/solution.cpp
@@ -11,7 +11,7 @@ struct TreeNode {
 };
 
 class Solution {
-  private:
+private:
     void traverse(std::vector<int> &list, TreeNode *root) {
         if (root == nullptr) {
             return;
@@ -22,7 +22,7 @@ class Solution {
         }
     }
 
-  public:
+public:
     std::vector<int> preorderTraversal(TreeNode *root) {
         std::vector<int> list;
         traverse(list, root);
diff --git a/Easy/contains-duplicate/solution.cpp b/Easy/contains-duplicate/solution.cpp
index 84b92c7..c05197b 100644
--- a/Easy/contains-duplicate/solution.cpp
+++ b/Easy/contains-duplicate/solution.cpp
@@ -1,3 +1,6 @@
+#include <unordered_set>
+#include <vector>
+
 class Solution {
 public:
     bool containsDuplicate(std::vector<int> &nums) {
diff --git a/Easy/excel-sheet-column-number/Solution.java b/Easy/excel-sheet-column-number/Solution.java
index 04b44a6..5446785 100644
--- a/Easy/excel-sheet-column-number/Solution.java
+++ b/Easy/excel-sheet-column-number/Solution.java
@@ -2,7 +2,7 @@ class Solution {
     public int titleToNumber(String ttl) {
         int num = 0;
         for (int i = 0; i < ttl.length(); i++)
-            num += Math.pow(26, i) * (int) (ttl.charAt(ttl.length() - i - 1) - 64);
+            num += Math.pow(26, i) * (int)(ttl.charAt(ttl.length() - i - 1) - 64);
 
         return num;
     }
diff --git a/Easy/excel-sheet-column-title/Solution.java b/Easy/excel-sheet-column-title/Solution.java
index e7d789b..7443903 100644
--- a/Easy/excel-sheet-column-title/Solution.java
+++ b/Easy/excel-sheet-column-title/Solution.java
@@ -2,9 +2,8 @@ class Solution {
     public String convertToTitle(int num) {
         StringBuilder ttl = new StringBuilder();
 
-        while (num > 0) {
-            --num;
-            char tba = (char) (num % 26 + 65);
+        while (num-- > 0) {
+            char tba = (char)(num % 26 + 65);
             ttl.insert(0, tba);
             num /= 26;
         }
diff --git a/Easy/first-unique-character-in-a-string/solution.cpp b/Easy/first-unique-character-in-a-string/solution.cpp
index 27aa156..6bd7406 100644
--- a/Easy/first-unique-character-in-a-string/solution.cpp
+++ b/Easy/first-unique-character-in-a-string/solution.cpp
@@ -2,7 +2,7 @@
 #include <unordered_set>
 
 class Solution {
-  public:
+public:
     /*
     int firstUniqChar(std::string line) {
         std::unordered_map<char, int[2]> hmap;
diff --git a/Easy/implement-queue-using-stacks/solution.cpp b/Easy/implement-queue-using-stacks/solution.cpp
index df5e166..fb167cb 100644
--- a/Easy/implement-queue-using-stacks/solution.cpp
+++ b/Easy/implement-queue-using-stacks/solution.cpp
@@ -1,11 +1,11 @@
 #include <stack>
 
 class MyQueue {
-  private:
+private:
     std::stack<int> shelfA;
     std::stack<int> shelfB;
 
-  public:
+public:
     MyQueue() {}
 
     void push(int data) { shelfA.push(data); }
diff --git a/Easy/intersection-of-two-arrays-ii/solution.cpp b/Easy/intersection-of-two-arrays-ii/solution.cpp
index dfa8a66..7b8ec89 100644
--- a/Easy/intersection-of-two-arrays-ii/solution.cpp
+++ b/Easy/intersection-of-two-arrays-ii/solution.cpp
@@ -1,5 +1,8 @@
+#include <algorithm>
+#include <vector>
+
 class Solution {
-  public:
+public:
     /*
     std::vector<int> intersect(std::vector<int> &nums1,
                                std::vector<int> &nums2) {
diff --git a/Easy/invert-binary-tree/solution.cpp b/Easy/invert-binary-tree/solution.cpp
index 0f085d1..cc006b3 100644
--- a/Easy/invert-binary-tree/solution.cpp
+++ b/Easy/invert-binary-tree/solution.cpp
@@ -9,7 +9,7 @@ struct TreeNode {
 };
 
 class Solution {
-  public:
+public:
     TreeNode *invertTree(TreeNode *root) {
         if (root != nullptr) {
             invertTree(root->left);
diff --git a/Easy/linked-list-cycle/solution.cpp b/Easy/linked-list-cycle/solution.cpp
index 1ce4d84..ea6ecca 100644
--- a/Easy/linked-list-cycle/solution.cpp
+++ b/Easy/linked-list-cycle/solution.cpp
@@ -8,7 +8,7 @@ struct ListNode {
 };
 
 class Solution {
-  public:
+public:
     // bool hasCycle(ListNode *head) {
     //     std::unordered_map<ListNode *, int> hmap;
     //     ListNode *curr = head;
diff --git a/Easy/maximum-depth-of-binary-tree/solution.cpp b/Easy/maximum-depth-of-binary-tree/solution.cpp
index 4939b86..ecaafad 100644
--- a/Easy/maximum-depth-of-binary-tree/solution.cpp
+++ b/Easy/maximum-depth-of-binary-tree/solution.cpp
@@ -9,11 +9,11 @@ struct TreeNode {
 };
 
 class Solution {
-  private:
-    void maxDepth(TreeNode *root, int index, int *max) {
+private:
+    void maxDepth(TreeNode *root, int index, int &max) {
         if (root == nullptr) {
-            if (index > *max) {
-                *max = index;
+            if (index > max) {
+                max = index;
             }
 
             return;
@@ -23,10 +23,10 @@ class Solution {
         }
     }
 
-  public:
+public:
     int maxDepth(TreeNode *root) {
         int max = 0;
-        maxDepth(root, 0, &max);
+        maxDepth(root, 0, max);
 
         return max;
     }
diff --git a/Easy/maximum-number-of-words-you-can-type/Solution.java b/Easy/maximum-number-of-words-you-can-type/Solution.java
index f84e316..923c709 100644
--- a/Easy/maximum-number-of-words-you-can-type/Solution.java
+++ b/Easy/maximum-number-of-words-you-can-type/Solution.java
@@ -5,14 +5,16 @@ class Solution {
         int ret = 0;
         for (boolean flag = true; words.hasMoreTokens(); flag = true) {
             String word = words.nextToken();
-            for (int i = 0; i < chars.length(); i++)
+            for (int i = 0; i < chars.length(); i++) {
                 if (word.indexOf(chars.charAt(i)) > -1) {
                     flag = false;
                     break;
                 }
+            }
 
-            if (flag)
+            if (flag) {
                 ++ret;
+            }
         }
 
         return ret;
diff --git a/Easy/maximum-subarray/solution.cpp b/Easy/maximum-subarray/solution.cpp
index 7532e7a..9278e68 100644
--- a/Easy/maximum-subarray/solution.cpp
+++ b/Easy/maximum-subarray/solution.cpp
@@ -1,5 +1,8 @@
+#include <cstdint>
+#include <vector>
+
 class Solution {
-  public:
+public:
     int maxSubArray(std::vector<int> &nums) {
         int max = INT32_MIN;
         int tmax = 0;
diff --git a/Easy/merge-sorted-array/solution.cpp b/Easy/merge-sorted-array/solution.cpp
index ed668be..273f480 100644
--- a/Easy/merge-sorted-array/solution.cpp
+++ b/Easy/merge-sorted-array/solution.cpp
@@ -1,5 +1,8 @@
+#include <algorithm>
+#include <vector>
+
 class Solution {
-  public:
+public:
     void merge(std::vector<int> &nums1, int m, std::vector<int> &nums2, int n) {
         for (int i = 0; i < n; ++i) {
             nums1[m + i] = nums2[i];
diff --git a/Easy/palindrome-number/solution.c b/Easy/palindrome-number/solution.c
index 205a06c..80cb50b 100644
--- a/Easy/palindrome-number/solution.c
+++ b/Easy/palindrome-number/solution.c
@@ -1,3 +1,5 @@
+#include <stdbool.h>
+
 bool isPalindrome(long int a) {
     if (a < 0)
         return false;
diff --git a/Easy/pascals-triangle/solution.cpp b/Easy/pascals-triangle/solution.cpp
index c55d27b..9adfb15 100644
--- a/Easy/pascals-triangle/solution.cpp
+++ b/Easy/pascals-triangle/solution.cpp
@@ -1,5 +1,7 @@
+#include <vector>
+
 class Solution {
-  public:
+public:
     std::vector<int> getRow(int n) {
         std::vector<int> prow = {1};
 
diff --git a/Easy/ransom-note/solution.cpp b/Easy/ransom-note/solution.cpp
index b17d0a2..0988327 100644
--- a/Easy/ransom-note/solution.cpp
+++ b/Easy/ransom-note/solution.cpp
@@ -2,7 +2,7 @@
 #include <unordered_map>
 
 class Solution {
-  public:
+public:
     bool canConstruct(std::string ransomNote, std::string magazine) {
         std::unordered_map<char, int> hmap[2];
 
diff --git a/Easy/remove-duplicates-from-sorted-array/solution.cpp b/Easy/remove-duplicates-from-sorted-array/solution.cpp
index 013dd1f..962e534 100644
--- a/Easy/remove-duplicates-from-sorted-array/solution.cpp
+++ b/Easy/remove-duplicates-from-sorted-array/solution.cpp
@@ -3,7 +3,7 @@
 #include <vector>
 
 class Solution {
-  public:
+public:
     int removeDuplicates(std::vector<int> &nums) {
         int k = 0, l = INT32_MIN;
         for (auto iter = nums.begin(); iter != nums.end(); iter.operator++()) {
diff --git a/Easy/remove-duplicates-from-sorted-list/solution.cpp b/Easy/remove-duplicates-from-sorted-list/solution.cpp
index aca39ba..b84a319 100644
--- a/Easy/remove-duplicates-from-sorted-list/solution.cpp
+++ b/Easy/remove-duplicates-from-sorted-list/solution.cpp
@@ -7,7 +7,7 @@ struct ListNode {
 };
 
 class Solution {
-  private:
+private:
     ListNode *removeElements(ListNode *head, int val) {
         if (head == nullptr) {
             return nullptr;
@@ -19,7 +19,7 @@ class Solution {
         }
     }
 
-  public:
+public:
     ListNode *deleteDuplicates(ListNode *head) {
         for (ListNode *curr = head; curr != nullptr && curr->next != nullptr;
              curr = curr->next) {
diff --git a/Easy/remove-linked-list-elements/solution.cpp b/Easy/remove-linked-list-elements/solution.cpp
index da56ddf..0f6ca27 100644
--- a/Easy/remove-linked-list-elements/solution.cpp
+++ b/Easy/remove-linked-list-elements/solution.cpp
@@ -7,7 +7,7 @@ struct ListNode {
 };
 
 class Solution {
-  public:
+public:
     ListNode *removeElements(ListNode *head, int val) {
         if (head == nullptr) {
             return nullptr;
diff --git a/Easy/repeated-substring-pattern/solution.cpp b/Easy/repeated-substring-pattern/solution.cpp
index e69de29..c42b2b0 100644
--- a/Easy/repeated-substring-pattern/solution.cpp
+++ b/Easy/repeated-substring-pattern/solution.cpp
@@ -0,0 +1,27 @@
+#include <string>
+
+class Solution {
+public:
+    bool repeatedSubstringPattern(std::string s) {
+        for (int i = 1; i <= s.size() / 2; ++i) {
+            std::string sl(s.substr(0, i));
+            if (s.size() % i == 0) {
+                bool found = false;
+                for (int j = 1; j < s.size() / i; ++j) {
+                    if (s.find(sl, sl.size() * j) == sl.size() * j) {
+                        found = true;
+                    } else {
+                        found = false;
+                        break;
+                    }
+                }
+
+                if (found) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+};
diff --git a/Easy/reshape-the-matrix/solution.cpp b/Easy/reshape-the-matrix/solution.cpp
index cbd1a9c..47c1c7e 100644
--- a/Easy/reshape-the-matrix/solution.cpp
+++ b/Easy/reshape-the-matrix/solution.cpp
@@ -1,5 +1,7 @@
+#include <vector>
+
 class Solution {
-  public:
+public:
     std::vector<std::vector<int>>
     matrixReshape(std::vector<std::vector<int>> &mat, int r, int c) {
         int m = mat.size(), n = mat[0].size();
diff --git a/Easy/reverse-linked-list/solution.cpp b/Easy/reverse-linked-list/solution.cpp
index b3addc7..b64ce4f 100644
--- a/Easy/reverse-linked-list/solution.cpp
+++ b/Easy/reverse-linked-list/solution.cpp
@@ -7,7 +7,7 @@ struct ListNode {
 };
 
 class Solution {
-  public:
+public:
     ListNode *reverseList(ListNode *head) {
         ListNode *prev = nullptr, *next = nullptr, *curr = head;
         while (curr != nullptr) {
diff --git a/Easy/search-in-a-binary-search-tree/solution.cpp b/Easy/search-in-a-binary-search-tree/solution.cpp
index 33f5b82..629b345 100644
--- a/Easy/search-in-a-binary-search-tree/solution.cpp
+++ b/Easy/search-in-a-binary-search-tree/solution.cpp
@@ -9,7 +9,7 @@ struct TreeNode {
 };
 
 class Solution {
-  public:
+public:
     TreeNode *searchBST(TreeNode *root, int val) {
         if (root == nullptr) {
             return nullptr;
diff --git a/Easy/two-sum/solution.cpp b/Easy/two-sum/solution.cpp
index 6b563ee..5e2833a 100644
--- a/Easy/two-sum/solution.cpp
+++ b/Easy/two-sum/solution.cpp
@@ -1,5 +1,8 @@
+#include <unordered_map>
+#include <vector>
+
 class Solution {
-  public:
+public:
     std::vector<int> twoSum(std::vector<int> &nums, int target) {
         std::unordered_map<int, int> hmap;
 
diff --git a/Easy/valid-anagram/solution.cpp b/Easy/valid-anagram/solution.cpp
index 858337b..881af82 100644
--- a/Easy/valid-anagram/solution.cpp
+++ b/Easy/valid-anagram/solution.cpp
@@ -2,7 +2,7 @@
 #include <unordered_map>
 
 class Solution {
-  public:
+public:
     bool isAnagram(std::string s, std::string t) {
         if (s.size() == t.size()) {
             std::unordered_map<char, int> hmap[2];
diff --git a/Easy/valid-parentheses/solution.cpp b/Easy/valid-parentheses/solution.cpp
index bee70fa..8159158 100644
--- a/Easy/valid-parentheses/solution.cpp
+++ b/Easy/valid-parentheses/solution.cpp
@@ -2,7 +2,7 @@
 #include <stack>
 
 class Solution {
-  public:
+public:
     bool isValid(std::string line) {
         std::stack<char> shelf;
         for (auto iter = line.begin(); iter != line.end(); iter.operator++()) {
diff --git a/Hard/longest-valid-parentheses/Solution.java b/Hard/longest-valid-parentheses/Solution.java
index 538073f..ad5b1c8 100644
--- a/Hard/longest-valid-parentheses/Solution.java
+++ b/Hard/longest-valid-parentheses/Solution.java
@@ -2,7 +2,7 @@ class Solution {
     public int longestValidParentheses(String str) {
         Stack<Integer> stack = new Stack<>();
         stack.push(-1);
-        
+
         int max = 0;
         for (int cur = 0; cur < str.length(); cur++) {
             if (str.charAt(cur) == '(') {
diff --git a/Hard/longest-valid-parentheses/solution.cpp b/Hard/longest-valid-parentheses/solution.cpp
index 64969f9..53bea27 100644
--- a/Hard/longest-valid-parentheses/solution.cpp
+++ b/Hard/longest-valid-parentheses/solution.cpp
@@ -2,7 +2,7 @@
 #include <string>
 
 class Solution {
-  public:
+public:
     int longestValidParentheses(std::string line) {
         std::stack<int> shelf;
         shelf.push(-1);
diff --git a/Hard/sudoku-solver/solution.cpp b/Hard/sudoku-solver/solution.cpp
index f5ee4de..0c5b9d8 100644
--- a/Hard/sudoku-solver/solution.cpp
+++ b/Hard/sudoku-solver/solution.cpp
@@ -2,7 +2,7 @@
 #include <vector>
 
 class Solution {
-  public:
+public:
     std::array<int, 2> nextEmpty(std::vector<std::vector<char>> &board) {
         for (int i = 0; i < 9; ++i) {
             for (int j = 0; j < 9; ++j) {
diff --git a/Medium/container-with-most-water/solution.cpp b/Medium/container-with-most-water/solution.cpp
index 942d9fc..b57bf58 100644
--- a/Medium/container-with-most-water/solution.cpp
+++ b/Medium/container-with-most-water/solution.cpp
@@ -2,7 +2,7 @@
 #include <vector>
 
 class Solution {
-  public:
+public:
     int maxArea(std::vector<int> &height) {
         int left = 0;
         int right = height.size() - 1;
diff --git a/Medium/insert-into-a-binary-search-tree/solution.cpp b/Medium/insert-into-a-binary-search-tree/solution.cpp
index c6612e5..cea89cc 100644
--- a/Medium/insert-into-a-binary-search-tree/solution.cpp
+++ b/Medium/insert-into-a-binary-search-tree/solution.cpp
@@ -9,7 +9,7 @@ struct TreeNode {
 };
 
 class Solution {
-  public:
+public:
     TreeNode *insertIntoBST(TreeNode *root, int val) {
         TreeNode *node = root;
         while (node != nullptr) {
diff --git a/Medium/letter-combinations-of-a-phone-number/solution.cpp b/Medium/letter-combinations-of-a-phone-number/solution.cpp
index d0c7afc..79aa617 100644
--- a/Medium/letter-combinations-of-a-phone-number/solution.cpp
+++ b/Medium/letter-combinations-of-a-phone-number/solution.cpp
@@ -2,9 +2,9 @@
 #include <vector>
 
 class Solution {
-  public:
+public:
     std::vector<std::string> letterCombinations(std::string digits) {
-        std::string letters[] = {"abc", "def",  "ghi", "jkl",
+        std::string letters[] = {"abc", "def", "ghi", "jkl",
                                  "mno", "pqrs", "tuv", "wxyz"};
 
         std::vector<std::string> finvec;
diff --git a/Medium/longest-palindromic-substring/solution.cpp b/Medium/longest-palindromic-substring/solution.cpp
index 1aba9f5..c4f7842 100644
--- a/Medium/longest-palindromic-substring/solution.cpp
+++ b/Medium/longest-palindromic-substring/solution.cpp
@@ -1,7 +1,7 @@
 #include <string>
 
 class Solution {
-  public:
+public:
     std::string longestPalindrome(std::string line) {
         if (line.size() < 2) {
             return line;
diff --git a/Medium/search-a-2d-matrix/solution.cpp b/Medium/search-a-2d-matrix/solution.cpp
index 42f4260..76f2b69 100644
--- a/Medium/search-a-2d-matrix/solution.cpp
+++ b/Medium/search-a-2d-matrix/solution.cpp
@@ -1,7 +1,7 @@
 #include <vector>
 
 class Solution {
-  private:
+private:
     bool binarySearch(std::vector<int> &nums, int start, int end, int target) {
         while (end >= start) {
             int middle = start + (end - start) / 2;
@@ -36,7 +36,7 @@ class Solution {
     }
     */
 
-  public:
+public:
     bool searchMatrix(std::vector<std::vector<int>> &matrix, int target) {
         int row = matrix.size();
         int col = matrix[0].size();
diff --git a/Medium/sort-list/solution.c b/Medium/sort-list/solution.c
index 7a923d9..fff1273 100644
--- a/Medium/sort-list/solution.c
+++ b/Medium/sort-list/solution.c
@@ -1,3 +1,10 @@
+#include <stdlib.h>
+
+struct ListNode {
+    int val;
+    struct ListNode *next;
+};
+
 struct ListNode *merge(struct ListNode *left, struct ListNode *right) {
     if (!left) {
         return right;
diff --git a/Medium/string-to-integer-atoi/solution.cpp b/Medium/string-to-integer-atoi/solution.cpp
index ee9fe03..a89a301 100644
--- a/Medium/string-to-integer-atoi/solution.cpp
+++ b/Medium/string-to-integer-atoi/solution.cpp
@@ -1,5 +1,7 @@
+#include <string>
+
 class Solution {
-  public:
+public:
     int myAtoi(std::string s) {
 
         unsigned long value = 0;
diff --git a/Medium/two-sum-ii-input-array-is-sorted/solution.cpp b/Medium/two-sum-ii-input-array-is-sorted/solution.cpp
index c7263e7..6f00c5b 100644
--- a/Medium/two-sum-ii-input-array-is-sorted/solution.cpp
+++ b/Medium/two-sum-ii-input-array-is-sorted/solution.cpp
@@ -1,5 +1,7 @@
+#include <vector>
+
 class Solution {
-  public:
+public:
     std::vector<int> twoSum(std::vector<int> &numbers, int target) {
         int j = -1;
         for (int i = 0; i < numbers.size(); ++i) {
@@ -8,14 +10,15 @@ class Solution {
             j = binarySearch(numbers, 0, numbers.size() - 1, otherhalf);
 
             if (j != -1 && i != j) {
-                if (i < j)
-                    return std::vector{i + 1, j + 1};
-                else
-                    return std::vector{j + 1, i + 1};
+                if (i < j) {
+                    return {i + 1, j + 1};
+                } else {
+                    return {j + 1, i + 1};
+                }
             }
         }
 
-        return std::vector{-1, -1};
+        return {-1, -1};
     }
 
     int binarySearch(std::vector<int> &numbers, int start, int end, int key) {