maximum-depth-of-binary-tree solution

Author: Yn3-3xh

maximum-depth-of-binary-tree/Yn3-3xh.java

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+/**
+[문제풀이]
+- 최대 depth 구하기
+- left or right의 null일 때 depth의 max 구하기
+- DFS 1
+time: O(N), space: O(N)
+    class Solution {
+        public int maxDepth(TreeNode root) {
+            return nextNode(root, 0);
+        }
+
+        private int nextNode(TreeNode node, int depth) {
+            if (node == null) {
+                return depth;
+            }
+
+            int leftDepth = nextNode(node.left, depth + 1);
+            int rightDepth = nextNode(node.right, depth + 1);
+            return Math.max(leftDepth, rightDepth);
+        }
+    }
+- DFS 2
+time: O(N), space: O(N)
+
+[회고]
+이전에 풀었던 Merget Two Sorted Lists 문제에서 주어진 메서드를 재사용할 수 있겠다는 생각으로 풀 수 있었다!
+ */
+
+/**
+ * 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 int maxDepth(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+
+        int leftDepth = maxDepth(root.left);
+        int rightDepth = maxDepth(root.right);
+        return Math.max(leftDepth, rightDepth) + 1;
+    }
+}
+