maximum depth of binary tree

Author: wad-jangjaejeong

maximum-depth-of-binary-tree/jaejeong1.java

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+/**
+ * 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 {
+  // 풀이 : DFS 탐색을 통해 리프 노드까지 탐색하면서 깊이를 계산한다.
+  // TC: O(N), SC: O(N)
+  int answer = 0;
+
+  public int maxDepth(TreeNode root) {
+    dfs(root, 1);
+
+    return answer;
+  }
+
+  private void dfs(TreeNode node, int depth) {
+    if (node == null) {
+      return;
+    }
+
+    if (depth > answer) {
+      answer = depth;
+    }
+
+    depth++;
+
+    dfs(node.left, depth);
+    dfs(node.right, depth);
+  }
+}