add new solutions

solutions/2/q236/solution.go

@@ -0,0 +1,31 @@
+package q236
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func lowestCommonAncestor(root, p, q *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	if root == p || root == q {
+		return root
+	}
+
+	l := lowestCommonAncestor(root.Left, p, q)
+	r := lowestCommonAncestor(root.Right, p, q)
+
+	switch {
+	case l == nil && r == nil:
+		return nil
+	case l != nil && r != nil:
+		return root
+	case l != nil:
+		return l
+	}
+	return r
+}
+
+var _ = lowestCommonAncestor