cs: add “700. Search in a Binary Search Tree”

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

cs/search-in-a-binary-tree.cs

@@ -0,0 +1,29 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public int val;
+ *     public TreeNode left;
+ *     public TreeNode right;
+ *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+public class Solution {
+    public TreeNode SearchBST(TreeNode root, int val) {
+        if (root == null) {
+            return null;
+        }
+
+        if (root.val == val) {
+            return root;
+        }
+
+        if (val < root.val) {
+            return SearchBST(root.left, val);
+        }
+        return SearchBST(root.right, val);
+    }
+}