Update README.md

Author: kamyu104

README.md

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-# [LeetCode](https://leetcode.com/problemset/algorithms/) ![Language](https://img.shields.io/badge/language-Python%20%2F%20C++%2011-orange.svg) [![License](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE.md) ![Update](https://img.shields.io/badge/update-weekly-green.svg) ![Progress](https://img.shields.io/badge/progress-961%20%2F%20961-ff69b4.svg) [![SayThanks](https://img.shields.io/badge/say-thanks-ff69f4.svg)](https://saythanks.io/to/kamyu104) ![Travis](https://travis-ci.org/kamyu104/LeetCode-Solutions.svg?branch=master)
+# [LeetCode](https://leetcode.com/problemset/algorithms/) ![Language](https://img.shields.io/badge/language-Python%20%2F%20C++%2011-orange.svg) [![License](https://img.shields.io/badge/license-MIT-blue.svg)](./LICENSE.md) ![Update](https://img.shields.io/badge/update-weekly-green.svg) ![Progress](https://img.shields.io/badge/progress-965%20%2F%20965-ff69b4.svg) [![SayThanks](https://img.shields.io/badge/say-thanks-ff69f4.svg)](https://saythanks.io/to/kamyu104) ![Travis](https://travis-ci.org/kamyu104/LeetCode-Solutions.svg?branch=master)
 
 * RIP to my old Leetcode repository, where there were ever `5.7k+` stars and `2.2k+` forks.  👼
 * Since free questions may be even mistakenly taken down by some companies, only solutions will be post on now.
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 951| [Flip Equivalent Binary Trees](https://leetcode.com/problems/flip-equivalent-binary-trees/) | [C++](./C++/flip-equivalent-binary-trees.cpp) [Python](./Python/flip-equivalent-binary-trees.py) | _O(n)_          | _O(h)_          | Medium           || DFS |
 958| [Check Completeness of a Binary Tree](https://leetcode.com/problems/check-completeness-of-a-binary-tree/) | [C++](./C++/check-completeness-of-a-binary-tree.cpp) [Python](./Python/check-completeness-of-a-binary-tree.py) | _O(n)_          | _O(w)_          | Medium           || BFS |
 965| [Univalued Binary Tree](https://leetcode.com/problems/univalued-binary-tree/) | [C++](./C++/univalued-binary-tree.cpp) [Python](./Python/univalued-binary-tree.py) | _O(n)_          | _O(h)_          | Easy           || DFS |
+971| [Flip Binary Tree To Match Preorder Traversal](https://leetcode.com/problems/flip-binary-tree-to-match-preorder-traversal/) | [C++](./C++/flip-binary-tree-to-match-preorder-traversal.cpp) [Python](./Python/flip-binary-tree-to-match-preorder-traversal.py) | _O(n)_          | _O(h)_          | Medium           || DFS |
 
 ## Hash Table
 |  #  | Title           |  Solution       |  Time           | Space           | Difficulty    | Tag          | Note| 
@@ -568,7 +569,8 @@
 910 | [Smallest Range II](https://leetcode.com/problems/smallest-range-ii/) | [C++](./C++/smallest-range-ii.cpp) [Python](./Python/smallest-range-ii.py) | _O(nlogn)_ | _O(1)_      | Medium         ||
 914 | [X of a Kind in a Deck of Cards](https://leetcode.com/problems/x-of-a-kind-in-a-deck-of-cards/) | [C++](./C++/x-of-a-kind-in-a-deck-of-cards.cpp) [Python](./Python/x-of-a-kind-in-a-deck-of-cards.py) | _O(n * (logn)^2)_ | _O(n)_      | Easy         ||
 963 | [Minimum Area Rectangle II](https://leetcode.com/problems/minimum-area-rectangle-ii/) | [C++](./C++/minimum-area-rectangle-ii.cpp) [Python](./Python/minimum-area-rectangle-ii.py) | _O(n^2)_ ~ _O(n^3)_ | _O(n^2)_      | Medium         ||
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+970 | [Powerful Integers](https://leetcode.com/problems/powerful-integers/) | [C++](./C++/powerful-integers.cpp) [Python](./Python/powerful-integers.py) | _O((logn)^2)_ | _O(r)_      | Easy         ||
+972 | [Equal Rational Numbers](https://leetcode.com/problems/equal-rational-numbers/) | [C++](./C++/equal-rational-numbers.cpp) [Python](./Python/equal-rational-numbers.py) | _O(1)_ | _O(1)_      | Hard         ||
 
 ## Sort
 |  #  | Title           |  Solution       |  Time           | Space           | Difficulty    | Tag          | Note| 
@@ -592,6 +594,7 @@
 451| [Sort Characters By Frequency](https://leetcode.com/problems/sort-characters-by-frequency/) | [C++](./C++/sort-characters-by-frequency.cpp) [Python](./Python/sort-characters-by-frequency.py) | _O(n)_ | _O(n)_        | Medium         | | |
 692| [Top K Frequent Words](https://leetcode.com/problems/top-k-frequent-words/) | [C++](./C++/top-k-frequent-words.cpp) [Python](./Python/top-k-frequent-words.py) | _O(n + klogk)_ on average | _O(n)_        | Medium         | | Quick Select, Heap, Bucket Sort |
 937| [Reorder Log Files](https://leetcode.com/problems/reorder-log-files/) | [C++](./C++/reorder-log-files.cpp) [Python](./Python/reorder-log-files.py) | _O(nlogn * l)_ | _O(l)_        | Easy         | | |
+969| [Pancake Sorting](https://leetcode.com/problems/pancake-sorting/) | [C++](./C++/pancake-sorting.cpp) [Python](./Python/pancake-sorting.py) | _O(n^2)_ | _O(l)_        | Medium         | | |
 
 ## Two Pointers
 |  #  | Title           |  Solution       |  Time           | Space           | Difficulty    | Tag          | Note|