diff --git a/Jongeun/Day10/100_SameTree.cpp b/Jongeun/Day10/100_SameTree.cpp
new file mode 100644
index 0000000..d0e0e84
--- /dev/null
+++ b/Jongeun/Day10/100_SameTree.cpp
@@ -0,0 +1,50 @@
+#include <iostream>
+
+using namespace std;
+
+struct TreeNode
+{
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode() : val(0), left(nullptr), right(nullptr) {}
+    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+};
+
+class Solution
+{
+public:
+    bool isSameTree(TreeNode *p, TreeNode *q)
+    {
+        if (p == nullptr && q == nullptr)
+        {
+            return true;
+        }
+
+        if (p->val == q->val)
+        {
+            if (isSameTree(p->left, q->left) && isSameTree(p->right, q->right))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+};
+
+int main()
+{
+    Solution isSameTree;
+    TreeNode *p = new TreeNode(1);
+    p->left = new TreeNode(2);
+    p->right = new TreeNode(1);
+    TreeNode *q = new TreeNode(1);
+    q->left = new TreeNode(1);
+    q->right = new TreeNode(2);
+
+    cout << isSameTree.isSameTree(p, q) << endl;
+
+    return 0;
+}
diff --git a/Jongeun/Day10/23_MergekSortedLists.cpp b/Jongeun/Day10/23_MergekSortedLists.cpp
new file mode 100644
index 0000000..4041204
--- /dev/null
+++ b/Jongeun/Day10/23_MergekSortedLists.cpp
@@ -0,0 +1,106 @@
+/**
+ * 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) {}
+ * };
+ */
+class Solution
+{
+public:
+    ListNode *mergeKLists(vector<ListNode *> &lists)
+    {
+        vector<ListNode *> list;
+        for (int i = 0; i < lists.size(); i++)
+        {
+            ListNode *cur = lists[i];
+            while (cur != nullptr)
+            {
+                list.push_back(cur);
+                cur = cur->next;
+            }
+        }
+
+        // sort the list
+        MergeSort(list, 0, list.size() - 1);
+
+        ListNode *sorted = new ListNode();
+        ListNode *tempt = sorted;
+
+        for (int i = 0; i < list.size(); i++)
+        {
+            tempt->next = list[i];
+            tempt = tempt->next;
+        }
+
+        return sorted->next;
+    }
+
+    void MergeSort(vector<ListNode *> &list, int low, int high)
+    {
+        if (low < high)
+        {
+            int mid = (low + high) / 2;
+            MergeSort(list, low, mid);
+            MergeSort(list, mid + 1, high);
+            Merge(list, low, mid, high);
+        }
+    }
+
+    void Merge(vector<ListNode *> &list, int low, int mid, int high)
+    {
+        int n1 = mid - low + 1;
+        int n2 = high - mid;
+
+        vector<ListNode *> leftArray;
+        leftArray.reserve(n1);
+        vector<ListNode *> rightArray;
+        rightArray.reserve(n2);
+
+        // copy data to tempt array
+        for (int i = 0; i < n1; i++)
+        {
+            leftArray[i] = list[low + i];
+        }
+        for (int i = 0; i < n2; i++)
+        {
+            rightArray[i] = list[mid + 1 + i];
+        }
+
+        // Merge the tempt array back into arr
+        int i = 0;
+        int j = 0;
+        int k = low;
+
+        while (i < n1 && j < n2)
+        {
+            if (leftArray[i]->val <= rightArray[j]->val)
+            {
+                list[k] = leftArray[i];
+                i++;
+            }
+            else
+            {
+                list[k] = rightArray[j];
+                j++;
+            }
+            k++;
+        }
+
+        while (i < n1)
+        {
+            list[k] = leftArray[i];
+            i++;
+            k++;
+        }
+        while (j < n2)
+        {
+            list[k] = rightArray[j];
+            j++;
+            k++;
+        }
+    }
+};
diff --git a/Jongeun/Day10/572_SubtreeofAnotherTree.cpp b/Jongeun/Day10/572_SubtreeofAnotherTree.cpp
new file mode 100644
index 0000000..4bc8f7d
--- /dev/null
+++ b/Jongeun/Day10/572_SubtreeofAnotherTree.cpp
@@ -0,0 +1,62 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution
+{
+public:
+    bool isSubtree(TreeNode *root, TreeNode *subRoot)
+    {
+        // check if it's the same as subtree
+        if (root == nullptr && subRoot == nullptr)
+        {
+            return true;
+        }
+        else if (root == nullptr || subRoot == nullptr)
+        {
+            return false;
+        }
+
+        if (root->val == subRoot->val)
+        {
+            bool isSub = _isSubtree(root->left, subRoot->left) && _isSubtree(root->right, subRoot->right);
+            if (isSub)
+            {
+                return true;
+            }
+        }
+        // else
+        return isSubtree(root->left, subRoot) || isSubtree(root->right, subRoot);
+    }
+
+    bool _isSubtree(TreeNode *root, TreeNode *subRoot)
+    {
+        // check if it's the same as subtree
+        if (root == nullptr && subRoot == nullptr)
+        {
+            return true;
+        }
+        else if (root == nullptr || subRoot == nullptr)
+        {
+            return false;
+        }
+
+        // none of both are nullptr
+
+        if (root->val == subRoot->val)
+        {
+            return _isSubtree(root->left, subRoot->left) && _isSubtree(root->right, subRoot->right);
+        }
+        else
+        {
+            return false;
+        }
+    }
+};