diff --git a/non-overlapping-intervals/dahyeong-yun.java b/non-overlapping-intervals/dahyeong-yun.java
new file mode 100644
index 0000000000..a82915da15
--- /dev/null
+++ b/non-overlapping-intervals/dahyeong-yun.java
@@ -0,0 +1,23 @@
+/**
+ * TC : O(n log n)
+ *   - intervals 배열의 길이 n 을 최초 정렬 하므로 O(n log n)
+ *   - 이후 for loop 는 O(n)
+ * SC : O(1)
+ *   - 별도 유의미한 공간 할당은 없음
+ */
+class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        Arrays.sort(intervals, (a, b) -> Integer.compare(a[1], b[1]));
+
+        int count = 1;
+        int beforeEnd = intervals[0][1];
+
+        for (int i = 1; i < intervals.length; i++) {
+            if (intervals[i][0] >= beforeEnd) {
+                count++;
+                beforeEnd = intervals[i][1];
+            }
+        }
+        return intervals.length - count;
+    }
+}
diff --git a/remove-nth-node-from-end-of-list/dahyeong-yun.java b/remove-nth-node-from-end-of-list/dahyeong-yun.java
new file mode 100644
index 0000000000..3f06731796
--- /dev/null
+++ b/remove-nth-node-from-end-of-list/dahyeong-yun.java
@@ -0,0 +1,32 @@
+/**
+ * TC: O(n)
+ *   - ListNode의 길이 n 만큰 순회하므로 O(n)
+ * SC: O(n)
+ *   - ListNode의 길이 n 만큼 ArrayList 할당하므로 O(n)
+ */
+class Solution {
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+        List<ListNode> list = new ArrayList<>();
+        ListNode cursor = head.next;
+        list.add(head);
+
+        while (cursor != null) {
+            list.add(cursor);
+            cursor = cursor.next;
+        }
+
+        int sz = list.size();
+        int deleteTarget = list.size() - n;
+        if (deleteTarget < 0)
+            return null;
+
+        if (deleteTarget - 1 >= 0 && deleteTarget <= sz - 2) {
+            list.get(deleteTarget - 1).next = list.get(deleteTarget + 1);
+        } else if(deleteTarget == 0) {
+            head = head.next;
+        } else {
+            list.get(deleteTarget - 1).next = null;
+        }
+        return head;
+    }
+}
diff --git a/same-tree/dahyeong-yun.java b/same-tree/dahyeong-yun.java
new file mode 100644
index 0000000000..5f3774fcf6
--- /dev/null
+++ b/same-tree/dahyeong-yun.java
@@ -0,0 +1,20 @@
+/**
+ * TC : O(n)
+ *   - TreeNode의 노드 수 n 만큼 순회하므로 O(n)
+ * SC : O(n)
+ *   - TreeNode의 노드 높이 h 만큼 콜스택이 쌓이고, 편향 트리의 경우 O(n) 까지 공간이 필요
+ */
+class Solution {
+    public boolean isSameTree(TreeNode p, TreeNode q) {
+        // p와 q 둘다 null 인가?
+        if(p == null && q == null) {
+            return true;
+        } else if(p == null || q == null) { // 하나만 null 인가
+            return false;
+        } else if(p.val != q.val) {
+            return false;
+        } else {
+            return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+        }
+    }
+}