Merge pull request #1012 from bus710/week10

[bus710] Week 10

Author: bus710

invert-binary-tree/bus710.go

@@ -0,0 +1,31 @@
+package hello
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func invertTree(root *TreeNode) *TreeNode {
+	if root == nil {
+		return root
+	}
+
+	visit(root)
+
+	return root
+}
+
+func visit(node *TreeNode) {
+	if node.Left != nil {
+		visit(node.Left)
+	}
+	if node.Right != nil {
+		visit(node.Right)
+	}
+
+	// Swap
+	tmp := node.Left
+	node.Left = node.Right
+	node.Right = tmp
+}