add wiki

Author: jackzhenguo

README.md

@@ -1,6 +1,8 @@
 # leetcode-csharp
 * Welcome to visit my CSDN blog(http://blog.csdn.net/daigualu) 
 * CSDN Column(http://blog.csdn.net/column/details/14761.html) where detail solutions are.
+## Leetcode-csharp Wiki
+[Wiki](https://github.com/jackzhenguo/leetcode-csharp/wiki)
 ## `Today Update`
 ### Math
 ####  7 Reverse Integer
@@ -241,4 +243,4 @@ Tags are following:
 *  Tips:
    * the most important function in solving this issue is 
        *  private TreeNode bulidTree(int preStart, int inStart, int inEnd) ;
-   * Plus, preStart index in preorder is the root index, which is also the separate point in inorder and it’s left is left subtree and right is right subtree.
+   * Plus, preStart index in preorder is the root index, which is also the separate point in inorder and it’s left is left subtree and right is right subtree.