maximum depth of binary tree solution

Author: radiantchoi

maximum-depth-of-binary-tree/radiantchoi.swift

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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func maxDepth(_ root: TreeNode?) -> Int {
+        var result = 0
+
+        traverse(root, 0, &result)
+
+        return result
+    }
+
+    func traverse(_ node: TreeNode?, _ current: Int, _ result: inout Int) {
+        guard let node else {
+            result = max(current, result)
+            return
+        }
+
+        let newCurrent = current + 1
+
+        traverse(node.left, newCurrent, &result)
+        traverse(node.right, newCurrent, &result)
+    }
+}