Add solution 543

Author: vulgur

543_DiameterOfBinaryTree.swift

@@ -0,0 +1,29 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+class Solution {
+    var m = 0
+    func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
+        guard let root = root else {return 0}
+        deep(node:root)
+        return m
+    }
+    
+    func deep(node:TreeNode?) -> Int {
+        guard let root = node else { return 0 }
+        let left = deep(node:root.left)
+        let right = deep(node:root.right)
+        m = max(m, left+right)
+        return max(left, right)+1
+    }
+}