diff --git a/README.md b/README.md
index 4fb918b0..cdf1df77 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ This book is notes about learning data structure and algorithm. It was written i
 ## Introduction
 
 1. Part I is some brief introduction of basic data structures and algorithm, such as linked lists, stack, queues, trees, sorting.
-2. Part II is the analysis and summary of programming problems, and most of the programming problems come from <https://leetcode.com/>, <http://www.lintcode.com/>, <http://www.geeksforgeeks.org/>, <http://hihocoder.com/>, <https://www.topcoder.com/>.
+2. Part II is the analysis and summary of programming problems, and most of the programming problems come from <https://leetcode.com/>, <http://www.lintcode.com/>, <http://www.geeksforgeeks.org/>, <http://hihocoder.com/>, <https://www.topcoder.com/>, <https://www.interviewbit.com/courses/programming/>.
 3. Part III is the appendix of resume and other supplements.
 
 This project is hosted on <https://github.com/billryan/algorithm-exercise> and rendered by [GitBook](https://www.gitbook.com/book/yuanbin/algorithm/details). You can star the repository on the GitHub to keep track of updates. Another choice is to subscribe channel `#github_commit` via Slack <https://ds-algo.slack.com/messages/github_commit/>.