Merge pull request #687 from openset/develop

Update: daily update

Author: Shuo

README.md

@@ -103,7 +103,7 @@ LeetCode Problems' Solutions
 | <span id="1182">1182</span> | [Shortest Distance to Target Color](https://leetcode.com/problems/shortest-distance-to-target-color "与目标颜色间的最短距离") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/shortest-distance-to-target-color) | Medium |
 | <span id="1181">1181</span> | [Before and After Puzzle](https://leetcode.com/problems/before-and-after-puzzle "前后拼接") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/before-and-after-puzzle) | Medium |
 | <span id="1180">1180</span> | [Count Substrings with Only One Distinct Letter](https://leetcode.com/problems/count-substrings-with-only-one-distinct-letter "统计只含单一字母的子串") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/count-substrings-with-only-one-distinct-letter) | Easy |
-| <span id="1179">1179</span> | [Reformat Department Table](https://leetcode.com/problems/reformat-department-table) | [MySQL](https://github.com/openset/leetcode/tree/master/problems/reformat-department-table) | Easy |
+| <span id="1179">1179</span> | [Reformat Department Table](https://leetcode.com/problems/reformat-department-table "重新格式化部门表") | [MySQL](https://github.com/openset/leetcode/tree/master/problems/reformat-department-table) | Easy |
 | <span id="1178">1178</span> | [Number of Valid Words for Each Puzzle](https://leetcode.com/problems/number-of-valid-words-for-each-puzzle "猜字谜") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-valid-words-for-each-puzzle) | Hard |
 | <span id="1177">1177</span> | [Can Make Palindrome from Substring](https://leetcode.com/problems/can-make-palindrome-from-substring "构建回文串检测") | [Go](https://github.com/openset/leetcode/tree/master/problems/can-make-palindrome-from-substring) | Medium |
 | <span id="1176">1176</span> | [Diet Plan Performance](https://leetcode.com/problems/diet-plan-performance "健身计划评估") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/diet-plan-performance) | Easy |

problems/additive-number/README.md

@@ -19,22 +19,32 @@
 
 <p><b>Note:</b> Numbers in the additive sequence <b>cannot</b> have leading zeros, so sequence <code>1, 2, 03</code> or <code>1, 02, 3</code> is invalid.</p>
 
-<p><b>Example 1:</b></p>
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
 
 <pre>
-<b>Input:</b> <code>&quot;112358&quot;</code>
-<b>Output:</b> true 
-<strong>Explanation: </strong>The digits can form an additive sequence: <code>1, 1, 2, 3, 5, 8</code>. 
+<strong>Input:</strong> &quot;112358&quot;
+<strong>Output:</strong> true
+<strong>Explanation:</strong> The digits can form an additive sequence: 1, 1, 2, 3, 5, 8. 
 &nbsp;            1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8
 </pre>
 
-<p><b>Example 2:</b></p>
+<p><strong>Example 2:</strong></p>
 
 <pre>
-<b>Input:</b> <code>&quot;199100199&quot;</code>
-<b>Output:</b> true 
-<strong>Explanation: </strong>The additive sequence is: <code>1, 99, 100, 199</code><span style="font-family: sans-serif, Arial, Verdana, &quot;Trebuchet MS&quot;;">.</span>&nbsp;
-&nbsp;            1 + 99 = 100, 99 + 100 = 199</pre>
+<strong>Input:</strong> &quot;199100199&quot;
+<strong>Output:</strong> true
+<strong>Explanation:</strong> The additive sequence is: 1, 99, 100, 199.&nbsp;
+&nbsp;            1 + 99 = 100, 99 + 100 = 199
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><font face="monospace"><code>num</code>&nbsp;</font>consists only of digits <code>&#39;0&#39;-&#39;9&#39;</code>.</li>
+	<li><code>1 &lt;= num.length &lt;= 35</code></li>
+</ul>
 
 <p><b>Follow up:</b><br />
 How would you handle overflow for very large input integers?</p>

problems/alphabet-board-path/README.md

@@ -46,3 +46,18 @@
 	<li><code>1 &lt;= target.length &lt;= 100</code></li>
 	<li><code>target</code> consists only of English lowercase letters.</li>
 </ul>
+
+### Related Topics
+  [[Hash Table](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)]
+  [[String](https://github.com/openset/leetcode/tree/master/tag/string/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+Create a hashmap from letter to position on the board.
+</details>
+
+<details>
+<summary>Hint 2</summary>
+Now for each letter, try moving there in steps, where at each step you check if it is inside the boundaries of the board.
+</details>

problems/binary-tree-coloring-game/README.md

@@ -42,3 +42,14 @@
 ### Related Topics
   [[Tree](https://github.com/openset/leetcode/tree/master/tag/tree/README.md)]
   [[Depth-first Search](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+The best move y must be immediately adjacent to x, since it locks out that subtree.
+</details>
+
+<details>
+<summary>Hint 2</summary>
+Can you count each of (up to) 3 different subtrees neighboring x?
+</details>

problems/brace-expansion-ii/README.md

@@ -31,7 +31,7 @@
 	<li>When we concatenate two expressions, we take the set of possible concatenations between two words where the first word comes from the first expression and the second word comes from the second expression.
 	<ul>
 		<li><code>R(&quot;{a,b}{c,d}&quot;) = {&quot;ac&quot;,&quot;ad&quot;,&quot;bc&quot;,&quot;bd&quot;}</code></li>
-		<li><code>R(&quot;{a{b,c}}{{d,e}f{g,h}}&quot;) = R(&quot;{ab,ac}{dfg,dfh,efg,efh}&quot;) = {&quot;abdfg&quot;, &quot;abdfh&quot;, &quot;abefg&quot;, &quot;abefh&quot;, &quot;acdfg&quot;, &quot;acdfh&quot;, &quot;acefg&quot;, &quot;acefh&quot;}</code></li>
+		<li><code>R(&quot;a{b,c}{d,e}f{g,h}&quot;)&nbsp;= {&quot;abdfg&quot;, &quot;abdfh&quot;, &quot;abefg&quot;, &quot;abefh&quot;, &quot;acdfg&quot;, &quot;acdfh&quot;, &quot;acefg&quot;, &quot;acefh&quot;}</code></li>
 	</ul>
 	</li>
 </ul>
@@ -52,8 +52,8 @@
 <p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Input: </strong><span id="example-input-1-1">&quot;{a,b}{c{d,e}}&quot;</span>
-<strong>Output: </strong><span id="example-output-1">[&quot;acd&quot;,&quot;ace&quot;,&quot;bcd&quot;,&quot;bce&quot;]</span>
+<strong>Input: </strong><span id="example-input-1-1">&quot;{a,b}{c,{d,e}}&quot;</span>
+<strong>Output: </strong><span id="example-output-1">[&quot;ac&quot;,&quot;ad&quot;,&quot;ae&quot;,&quot;bc&quot;,&quot;bd&quot;,&quot;be&quot;]</span>
 </pre>
 
 <div>
@@ -70,7 +70,7 @@
 <p><strong>Constraints:</strong></p>
 
 <ol>
-	<li><code>1 &lt;= expression.length &lt;= 50</code></li>
+	<li><code>1 &lt;= expression.length &lt;= 60</code></li>
 	<li><code>expression[i]</code> consists of <code>&#39;{&#39;</code>, <code>&#39;}&#39;</code>, <code>&#39;,&#39;</code>or lowercase English letters.</li>
 	<li>The given&nbsp;<code>expression</code>&nbsp;represents a set of words based on the grammar given in the description.</li>
 </ol>

problems/building-h2o/README.md

@@ -9,9 +9,9 @@
 
 [Next >](https://github.com/openset/leetcode/tree/master/problems/number-of-days-in-a-month "Number of Days in a Month")
 
-## [1117. Building H2O (Hard)](https://leetcode.com/problems/building-h2o "H2O 生成")
+## [1117. Building H2O (Medium)](https://leetcode.com/problems/building-h2o "H2O 生成")
 
-<p>There are two kinds of threads, <code>oxygen</code> and <code>hydrogen</code>. Your goal is to group these threads to form water molecules.&nbsp;There is a barrier where each thread has to&nbsp;wait until a complete molecule can be formed. Hydrogen and oxygen threads will be given a <code>releaseHydrogen</code>&nbsp;and <code>releaseOxygen</code>&nbsp;method respectfully, which will allow them to pass the barrier. These threads should pass the barrier in groups of three, and they must be able to immediately bond with each other to form a water molecule.&nbsp;You must guarantee that all the threads from one molecule bond <em>before</em> any other threads from the next molecule do.</p>
+<p>There are two kinds of threads, <code>oxygen</code> and <code>hydrogen</code>. Your goal is to group these threads to form water molecules.&nbsp;There is a barrier where each thread has to&nbsp;wait until a complete molecule can be formed. Hydrogen and oxygen threads will be given <code>releaseHydrogen</code>&nbsp;and <code>releaseOxygen</code>&nbsp;methods respectively, which will allow them to pass the barrier. These threads should pass the barrier in groups of three, and they must be able to immediately bond with each other to form a water molecule.&nbsp;You must guarantee that all the threads from one molecule bond <em>before</em> any other threads from the next molecule do.</p>
 
 <p>In other words:</p>
 
@@ -20,6 +20,8 @@
 	<li>If a hydrogen thread arrives at the barrier when no other threads are present, it has to wait for an oxygen thread and another hydrogen thread.</li>
 </ul>
 
+<p>We don&rsquo;t have to worry about matching the threads up explicitly; that is, the threads do not necessarily know which other threads they are paired up with. The key is just that threads pass the barrier in complete sets; thus, if we examine the sequence of threads that bond and divide them into groups of three, each group should contain one oxygen and two hydrogen threads.</p>
+
 <p>Write synchronization code for oxygen and hydrogen molecules that enforces these constraints.</p>
 
 <div>
@@ -50,7 +52,7 @@
 <p><strong>Constraints:</strong></p>
 
 <ul>
-	<li>Total length of input string will be 3<em>n</em>, where 1 &le;&nbsp;<em>n</em>&nbsp;&le; 50.</li>
+	<li>Total length of input string will be 3<em>n</em>, where 1 &le;&nbsp;<em>n</em>&nbsp;&le; 20.</li>
 	<li>Total number of <code>H</code> will be 2<em>n</em>&nbsp;in the input string.</li>
 	<li>Total number of <code>O</code> will&nbsp;be <em>n</em>&nbsp;in the input&nbsp;string.</li>
 </ul>

problems/bulls-and-cows/README.md

@@ -9,7 +9,7 @@
 
 [Next >](https://github.com/openset/leetcode/tree/master/problems/longest-increasing-subsequence "Longest Increasing Subsequence")
 
-## [299. Bulls and Cows (Medium)](https://leetcode.com/problems/bulls-and-cows "猜数字游戏")
+## [299. Bulls and Cows (Easy)](https://leetcode.com/problems/bulls-and-cows "猜数字游戏")
 
 <p>You are playing the following <a href="https://en.wikipedia.org/wiki/Bulls_and_Cows" target="_blank">Bulls and Cows</a> game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called &quot;bulls&quot;) and how many digits match the secret number but locate in the wrong position (called &quot;cows&quot;). Your friend will use successive guesses and hints to eventually derive the secret number.</p>
 

problems/corporate-flight-bookings/README.md

@@ -33,3 +33,7 @@
 	<li><code>1 &lt;= bookings[i][0] &lt;= bookings[i][1] &lt;= n &lt;= 20000</code></li>
 	<li><code>1 &lt;= bookings[i][2] &lt;= 10000</code></li>
 </ul>
+
+### Related Topics
+  [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+  [[Math](https://github.com/openset/leetcode/tree/master/tag/math/README.md)]

problems/count-vowels-permutation/README.md

@@ -9,7 +9,7 @@
 
 Next >
 
-## [5216. Count Vowels Permutation (Hard)](https://leetcode.com/problems/count-vowels-permutation "统计元音字母序列的数目")
+## [1220. Count Vowels Permutation (Hard)](https://leetcode.com/problems/count-vowels-permutation "统计元音字母序列的数目")
 
 <p>Given an integer <code>n</code>, your task is to count how many strings of length <code>n</code> can be formed under the following rules:</p>
 
@@ -54,6 +54,9 @@ Next >
 	<li><code>1 &lt;= n &lt;= 2 * 10^4</code></li>
 </ul>
 
+### Related Topics
+  [[Dynamic Programming](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)]
+
 ### Hints
 <details>
 <summary>Hint 1</summary>

problems/critical-connections-in-a-network/README.md

@@ -38,6 +38,9 @@
 	<li>There are no repeated connections.</li>
 </ul>
 
+### Related Topics
+  [[Depth-first Search](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)]
+
 ### Hints
 <details>
 <summary>Hint 1</summary>