update doc

Author: jinshendan

README.md

@@ -15,6 +15,9 @@ Solutions in various programming languages are provided. Enjoy it.
 5. [Random Pick With Weight](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/05-Random-Pick-With-Weight): Binary Search + Probability
 6. [Queue Reconstruction by Height](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/06-Queue-Reconstruction-By-Height): Greedy
 7. [Coin Change 2](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/07-Coin-Change-2): DP
+8. [Power of Two](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/08-Power-Of-Two): Bitwise manipulation
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 ## May LeetCoding Challenge