Adding 543. Diameter of Binary Tree in Swift

Author: Mahim1997

swift/543-Diameter-of-Binary-Tree.swift

@@ -0,0 +1,40 @@
+/**
+ * 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 {
+    private var globalMaxDiameter: Int = 0
+    
+    // Additionally, update the globalDiameter here
+    func getMaxDepth(_ node: TreeNode?) -> Int {
+        guard let node = node else { return 0 }
+        
+        // compute for each child
+        let leftMax = getMaxDepth(node.left)
+        let rightMax = getMaxDepth(node.right)
+        
+        // update diameter
+        let diameter = leftMax + rightMax
+        self.globalMaxDiameter = max(self.globalMaxDiameter, diameter)
+        
+        // return max depth of 'this' node
+        return 1 + max(leftMax, rightMax)        
+    }
+    
+    func diameterOfBinaryTree(_ root: TreeNode?) -> Int {
+        self.globalMaxDiameter = 0
+        getMaxDepth(root)
+        return self.globalMaxDiameter
+    }
+}