From e44e93b974dbcc363588a2b78dfadeb62808c0a9 Mon Sep 17 00:00:00 2001
From: hyerijung <hyerijung0903@gmail.com>
Date: Sun, 24 May 2026 14:57:38 +0900
Subject: [PATCH 1/3] same-tree solutions

---
 same-tree/hyeri0903.java | 44 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 same-tree/hyeri0903.java

diff --git a/same-tree/hyeri0903.java b/same-tree/hyeri0903.java
new file mode 100644
index 0000000000..56a62885bd
--- /dev/null
+++ b/same-tree/hyeri0903.java
@@ -0,0 +1,44 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+    public boolean isSameTree(TreeNode p, TreeNode q) {
+        /**
+        1.problem: 2개의 bst 가 동일한지 체크
+        2.constraints - 구조와 노드가 동일해야된다
+        3.solution - DFS
+        1) 두 트리의 노드가 모두 null -> true
+        2) 둘중 하나만 null -> false
+        3) 값이 다르면 false
+        4)재귀로 트리의 구조가 동일한지 체크
+         */
+
+         if(p == null && q == null) {
+            return true;
+         }
+         if(p == null || q == null) {
+            return false;
+         }
+        if(p.val != q.val) {
+            return false;
+        }
+
+        if(isSameTree(p.left, q.left) && isSameTree(p.right, q.right)) {
+            return true;
+        }
+        return false;
+    }
+
+}

From 2b0651197a7eaf44f5208d203ea61342b7d9f32e Mon Sep 17 00:00:00 2001
From: hyerijung <hyerijung0903@gmail.com>
Date: Sun, 24 May 2026 15:20:26 +0900
Subject: [PATCH 2/3] remove-nth-node-from-end-of-list

---
 .../hyeri0903.java                            | 46 +++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 remove-nth-node-from-end-of-list/hyeri0903.java

diff --git a/remove-nth-node-from-end-of-list/hyeri0903.java b/remove-nth-node-from-end-of-list/hyeri0903.java
new file mode 100644
index 0000000000..04644193ba
--- /dev/null
+++ b/remove-nth-node-from-end-of-list/hyeri0903.java
@@ -0,0 +1,46 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public ListNode removeNthFromEnd(ListNode head, int n) {
+        /**
+        1.linked list 에서 뒤에서 n번째 node remove
+        2.constraints:
+        node 개수(sz) min=1, max=30
+        n값  min = 1, max= sz
+        3.solutions: two pointers
+        - fast, slow pointer 2개의 간격 = n
+        - fast 가 끝지점에 도달하면 그때 slow.next 를 제거
+        time: O(n), space: O(1)
+         */
+
+         ListNode dummy = new ListNode(0);
+         dummy.next = head;
+
+         ListNode fast = dummy;
+         ListNode slow = dummy;
+
+         //fast pointer n+1칸 이동, fast - slow = n
+         for(int i = 0; i <= n; i++) {
+            fast = fast.next; 
+         }
+
+         while(fast != null) {
+            fast = fast.next;
+            slow = slow.next;
+         }
+
+         //slow pointer 의 다음 노드(slow.next) 제거
+         slow.next = slow.next.next;
+
+         return dummy.next;
+        
+    }
+}

From 33aeb1d27564ee378e896a65e0ad95bbad8eada8 Mon Sep 17 00:00:00 2001
From: hyerijung <hyerijung0903@gmail.com>
Date: Sun, 24 May 2026 15:49:55 +0900
Subject: [PATCH 3/3] non overlapping intervals solutions

---
 non-overlapping-intervals/hyeri0903.java | 30 ++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 non-overlapping-intervals/hyeri0903.java

diff --git a/non-overlapping-intervals/hyeri0903.java b/non-overlapping-intervals/hyeri0903.java
new file mode 100644
index 0000000000..ac8c8077b9
--- /dev/null
+++ b/non-overlapping-intervals/hyeri0903.java
@@ -0,0 +1,30 @@
+class Solution {
+    public int eraseOverlapIntervals(int[][] intervals) {
+        /**
+        1.prob: 겹치지 않는 최소한의 non-oerlapping interval 제거
+        2.constraints
+        - inverval.lenght min=1, max = 100,000
+        3.solutions - Greedy
+        - end 기준 오름차순 정렬
+        - 이전 interval end 저장
+        - 다음 interval check, 안겹치면 -> 선택, 겹치면 count++
+        Time: O(n logn), Space: O(1)
+         */
+         int count = 0;
+    
+         //end 기준 ascending 정렬
+         Arrays.sort(intervals, (a, b) -> a[1] - b[1]);
+          int end = intervals[0][1];
+
+         //겹치면 count++, 안겹치면 end update
+         for(int i = 1; i < intervals.length; i++) {
+                if(intervals[i][0] < end) {
+                    count++;
+                } else {
+                    end = intervals[i][1];
+                }
+         }
+
+        return count;
+    }
+}