add: soma-tree, remove-nth-node

Author: Yongseok-Choi-dev

remove-nth-node-from-end-of-list/YoungSeok-Choi.java

@@ -0,0 +1,48 @@
+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) {
+        int length = 0;
+        ListNode cur = head;
+
+        while (cur != null) {
+            cur = cur.next;
+            length++;
+        }
+
+        int start = 1;
+        int targetIdx = length - n + 1;
+        ListNode result = new ListNode(-1);
+        ListNode c = result;
+
+        while (head != null) {
+            if (targetIdx == start) {
+                head = head.next;
+                start++;
+                continue;
+            }
+
+            c.next = new ListNode(head.val);
+            c = c.next;
+            start++;
+            head = head.next;
+        }
+
+        return result.next;
+    }
+}

same-tree/YoungSeok-Choi.java

@@ -0,0 +1,34 @@
+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) {
+
+        if (p == null && q == null) {
+            return true;
+        }
+
+        if (p == null || q == null || q.val != p.val) {
+            return false;
+        }
+
+        // 특정 깊이의 Node 가 같다면 null을 만날때 까지 탐색하고, 같지 않다면 바로 false를 반환.
+        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
+    }
+}