go: add «543. Diameter of Binary Tree»

Signed-off-by: Matej Focko <mfocko@redhat.com>

go/diameter-of-binary-tree.go

@@ -0,0 +1,29 @@
+package diameter_of_binary_tree
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func diameterAndHeight(node *TreeNode) (int, int) {
+	if node == nil {
+		return 0, 0
+	}
+
+	leftDiameter, leftHeight := diameterAndHeight(node.Left)
+	rightDiameter, rightHeight := diameterAndHeight(node.Right)
+
+	diameter := max(leftHeight+rightHeight, max(leftDiameter, rightDiameter))
+	height := 1 + max(leftHeight, rightHeight)
+
+	return diameter, height
+}
+
+func diameterOfBinaryTree(root *TreeNode) int {
+	diameter, _ := diameterAndHeight(root)
+	return diameter
+}