add code of 236 and fix bug on 235

Author: Li Li

top-interview-questions/235. Lowest Common Ancestor of a Binary Search Tree.cs

@@ -2,12 +2,11 @@
 public class Solution {
     public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
         if (root == null) return null;
-        if (root.val == p.val || root.val == q.val) return root;
+        if (root == p || root == q) return root;
         TreeNode left = LowestCommonAncestor(root.left, p, q);
         TreeNode right = LowestCommonAncestor(root.right, p, q);
         if (left != null && right != null) return root;
-        else if (left == null) return right;
-        else return left;
+        return left == null ? right : left;
     }
 }
 

top-interview-questions/236. Lowest Common Ancestor of a Binary Tree.cs

@@ -0,0 +1,10 @@
+public class Solution {
+    public TreeNode LowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
+        if (root == null) return null;
+        if (root == p || root == q) return root;
+        TreeNode left = LowestCommonAncestor(root.left, p, q);
+        TreeNode right = LowestCommonAncestor(root.right, p, q);
+        if (left != null && right != null) return root;
+        return left == null ? right : left;
+    }
+}