A: new

Author: Shuo

README.md

@@ -11,34 +11,41 @@
 
 ## [717. 1-bit and 2-bit Characters (Easy)](https://leetcode.com/problems/1-bit-and-2-bit-characters "1比特与2比特字符")
 
-<p>We have two special characters. The first character can be represented by one bit <code>0</code>. The second character can be represented by two bits (<code>10</code> or <code>11</code>).  </p>
+<p>We have two special characters:</p>
 
-<p>Now given a string represented by several bits. Return whether the last character must be a one-bit character or not. The given string will always end with a zero.</p>
+<ul>
+	<li>The first character can be represented by one bit <code>0</code>.</li>
+	<li>The second character can be represented by two bits (<code>10</code> or <code>11</code>).</li>
+</ul>
+
+<p>Given a binary array <code>bits</code> that ends with <code>0</code>, return <code>true</code> if the last character must be a one-bit character.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
 
-<p><b>Example 1:</b><br />
 <pre>
-<b>Input:</b> 
-bits = [1, 0, 0]
-<b>Output:</b> True
-<b>Explanation:</b> 
-The only way to decode it is two-bit character and one-bit character. So the last character is one-bit character.
+<strong>Input:</strong> bits = [1,0,0]
+<strong>Output:</strong> true
+<strong>Explanation:</strong> The only way to decode it is two-bit character and one-bit character.
+So the last character is one-bit character.
 </pre>
-</p>
 
-<p><b>Example 2:</b><br />
+<p><strong>Example 2:</strong></p>
+
 <pre>
-<b>Input:</b> 
-bits = [1, 1, 1, 0]
-<b>Output:</b> False
-<b>Explanation:</b> 
-The only way to decode it is two-bit character and two-bit character. So the last character is NOT one-bit character.
+<strong>Input:</strong> bits = [1,1,1,0]
+<strong>Output:</strong> false
+<strong>Explanation:</strong> The only way to decode it is two-bit character and two-bit character.
+So the last character is not one-bit character.
 </pre>
-</p>
 
-<p><b>Note:</b>
-<li><code>1 <= len(bits) <= 1000</code>.</li>
-<li><code>bits[i]</code> is always <code>0</code> or <code>1</code>.</li>
-</p>
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= bits.length &lt;= 1000</code></li>
+	<li><code>bits[i]</code> is either <code>0</code> or <code>1</code>.</li>
+</ul>
 
 ### Related Topics
   [[Array](../../tag/array/README.md)]

problems/1-bit-and-2-bit-characters/README.md

@@ -15,8 +15,6 @@
 
 <p>Return <em><code>true</code> if there is a <strong>132 pattern</strong> in <code>nums</code>, otherwise, return <code>false</code>.</em></p>
 
-<p><strong>Follow up: </strong>The <code>O(n^2)</code> is trivial, could you come up with the <code>O(n logn)</code> or the <code>O(n)</code> solution?</p>
-
 <p>&nbsp;</p>
 <p><strong>Example 1:</strong></p>
 
@@ -47,7 +45,7 @@
 
 <ul>
 	<li><code>n == nums.length</code></li>
-	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
+	<li><code>1 &lt;= n &lt;= 2 * 10<sup>5</sup></code></li>
 	<li><code>-10<sup>9</sup> &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
 </ul>
 

problems/132-pattern/README.md

@@ -9,6 +9,6 @@
 
 [Next >](../minimum-path-cost-in-a-hidden-grid "Minimum Path Cost in a Hidden Grid")
 
-## [1809. Ad-Free Sessions (Easy)](https://leetcode.com/problems/ad-free-sessions "")
+## [1809. Ad-Free Sessions (Easy)](https://leetcode.com/problems/ad-free-sessions "没有广告的剧集")
 
 

problems/ad-free-sessions/README.md

@@ -11,50 +11,57 @@
 
 ## [816. Ambiguous Coordinates (Medium)](https://leetcode.com/problems/ambiguous-coordinates "模糊坐标")
 
-<p>We had some 2-dimensional coordinates, like <code>&quot;(1, 3)&quot;</code> or <code>&quot;(2, 0.5)&quot;</code>.&nbsp; Then, we removed&nbsp;all commas, decimal points, and spaces, and ended up with the string&nbsp;<code>s</code>.&nbsp; Return a list of strings representing&nbsp;all possibilities for what our original coordinates could have been.</p>
+<p>We had some 2-dimensional coordinates, like <code>&quot;(1, 3)&quot;</code> or <code>&quot;(2, 0.5)&quot;</code>. Then, we removed all commas, decimal points, and spaces and ended up with the string s.</p>
 
-<p>Our original representation never had extraneous zeroes, so we never started with numbers like &quot;00&quot;, &quot;0.0&quot;, &quot;0.00&quot;, &quot;1.0&quot;, &quot;001&quot;, &quot;00.01&quot;, or any other number that can be represented with&nbsp;less digits.&nbsp; Also, a decimal point within a number never occurs without at least one digit occuring before it, so we never started with numbers like &quot;.1&quot;.</p>
+<ul>
+	<li>For example, <code>&quot;(1, 3)&quot;</code> becomes <code>s = &quot;(13)&quot;</code> and <code>&quot;(2, 0.5)&quot;</code> becomes <code>s = &quot;(205)&quot;</code>.</li>
+</ul>
+
+<p>Return <em>a list of strings representing all possibilities for what our original coordinates could have been</em>.</p>
+
+<p>Our original representation never had extraneous zeroes, so we never started with numbers like <code>&quot;00&quot;</code>, <code>&quot;0.0&quot;</code>, <code>&quot;0.00&quot;</code>, <code>&quot;1.0&quot;</code>, <code>&quot;001&quot;</code>, <code>&quot;00.01&quot;</code>, or any other number that can be represented with fewer digits. Also, a decimal point within a number never occurs without at least one digit occurring before it, so we never started with numbers like <code>&quot;.1&quot;</code>.</p>
 
-<p>The final answer list can be returned in any order.&nbsp; Also note that all coordinates in the final answer&nbsp;have exactly one space between them (occurring after the comma.)</p>
+<p>The final answer list can be returned in any order. All coordinates in the final answer have exactly one space between them (occurring after the comma.)</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Example 1:</strong>
 <strong>Input:</strong> s = &quot;(123)&quot;
-<strong>Output:</strong> [&quot;(1, 23)&quot;, &quot;(12, 3)&quot;, &quot;(1.2, 3)&quot;, &quot;(1, 2.3)&quot;]
+<strong>Output:</strong> [&quot;(1, 2.3)&quot;,&quot;(1, 23)&quot;,&quot;(1.2, 3)&quot;,&quot;(12, 3)&quot;]
 </pre>
 
+<p><strong>Example 2:</strong></p>
+
 <pre>
-<strong>Example 2:</strong>
-<strong>Input:</strong> s = &quot;(00011)&quot;
-<strong>Output:</strong> &nbsp;[&quot;(0.001, 1)&quot;, &quot;(0, 0.011)&quot;]
-<strong>Explanation:</strong> 
-0.0, 00, 0001 or 00.01 are not allowed.
+<strong>Input:</strong> s = &quot;(0123)&quot;
+<strong>Output:</strong> [&quot;(0, 1.23)&quot;,&quot;(0, 12.3)&quot;,&quot;(0, 123)&quot;,&quot;(0.1, 2.3)&quot;,&quot;(0.1, 23)&quot;,&quot;(0.12, 3)&quot;]
+<strong>Explanation:</strong> 0.0, 00, 0001 or 00.01 are not allowed.
 </pre>
 
+<p><strong>Example 3:</strong></p>
+
 <pre>
-<strong>Example 3:</strong>
-<strong>Input:</strong> s = &quot;(0123)&quot;
-<strong>Output:</strong> [&quot;(0, 123)&quot;, &quot;(0, 12.3)&quot;, &quot;(0, 1.23)&quot;, &quot;(0.1, 23)&quot;, &quot;(0.1, 2.3)&quot;, &quot;(0.12, 3)&quot;]
+<strong>Input:</strong> s = &quot;(00011)&quot;
+<strong>Output:</strong> [&quot;(0, 0.011)&quot;,&quot;(0.001, 1)&quot;]
 </pre>
 
+<p><strong>Example 4:</strong></p>
+
 <pre>
-<strong>Example 4:</strong>
 <strong>Input:</strong> s = &quot;(100)&quot;
-<strong>Output:</strong> [(10, 0)]
-<strong>Explanation:</strong> 
-1.0 is not allowed.
+<strong>Output:</strong> [&quot;(10, 0)&quot;]
+<strong>Explanation:</strong> 1.0 is not allowed.
 </pre>
 
 <p>&nbsp;</p>
-
-<p><strong>Note: </strong></p>
+<p><strong>Constraints:</strong></p>
 
 <ul>
-	<li><code>4 &lt;= s.length &lt;= 12</code>.</li>
-	<li><code>s[0]</code> = &quot;(&quot;, <code>s[s.length - 1]</code> = &quot;)&quot;, and the other elements in <code>s</code> are digits.</li>
+	<li><code>4 &lt;= s.length &lt;= 12</code></li>
+	<li><code>s[0] == &#39;(&#39;</code> and <code>s[s.length - 1] == &#39;)&#39;</code>.</li>
+	<li>The rest of <code>s</code> are digits.</li>
 </ul>
 
-<p>&nbsp;</p>
-
 ### Related Topics
   [[String](../../tag/string/README.md)]

problems/ambiguous-coordinates/README.md

@@ -13,7 +13,7 @@
 
 <p>You are given an integer array <code>nums</code> of length <code>n</code> where <code>nums</code> is a permutation of the numbers in the range <code>[0, n - 1]</code>.</p>
 
-<p>You should build a set <code>s[k] = {nums[k], nums[nums[i]], nums[nums[nums[k]]], ... }</code> subjected to the following rule:</p>
+<p>You should build a set <code>s[k] = {nums[k], nums[nums[k]], nums[nums[nums[k]]], ... }</code> subjected to the following rule:</p>
 
 <ul>
 	<li>The first element in <code>s[k]</code> starts with the selection of the element <code>nums[k]</code> of <code>index = k</code>.</li>

problems/array-nesting/README.md

@@ -54,7 +54,7 @@
 <p><strong>Constraints:</strong></p>
 
 <ul>
-	<li><code>2 &lt;= asteroids.length&nbsp;&lt;= 10<sup>4</sup></code></li>
+	<li><code>2 &lt;= asteroids.length &lt;= 10<sup>4</sup></code></li>
 	<li><code>-1000 &lt;= asteroids[i] &lt;= 1000</code></li>
 	<li><code>asteroids[i] != 0</code></li>
 </ul>

problems/asteroid-collision/README.md

@@ -11,9 +11,9 @@
 
 ## [224. Basic Calculator (Hard)](https://leetcode.com/problems/basic-calculator "基本计算器")
 
-<p>Given a string <code>s</code> representing an expression, implement a basic calculator to evaluate it.</p>
+<p>Given a string <code>s</code> representing a valid expression, implement a basic calculator to evaluate it, and return <em>the result of the evaluation</em>.</p>
 
-<p><b data-stringify-type="bold">Note:&nbsp;</b>You are not allowed to use any built-in function which evaluates strings as mathematical expressions, such as&nbsp;<code data-stringify-type="code">eval()</code>.</p>
+<p><strong>Note:</strong> You are <strong>not</strong> allowed to use any built-in function which evaluates strings as mathematical expressions, such as <code>eval()</code>.</p>
 
 <p>&nbsp;</p>
 <p><strong>Example 1:</strong></p>
@@ -37,13 +37,22 @@
 <strong>Output:</strong> 23
 </pre>
 
+<p><strong>Example 4:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;+48 + -48&quot;
+<strong>Output:</strong> 0
+<strong>Explanation:</strong>&nbsp;Numbers can have multiple digits and start with +/-.
+</pre>
+
 <p>&nbsp;</p>
 <p><strong>Constraints:</strong></p>
 
 <ul>
 	<li><code>1 &lt;= s.length &lt;= 3&nbsp;* 10<sup>5</sup></code></li>
 	<li><code>s</code> consists of digits, <code>&#39;+&#39;</code>, <code>&#39;-&#39;</code>, <code>&#39;(&#39;</code>, <code>&#39;)&#39;</code>, and <code>&#39; &#39;</code>.</li>
 	<li><code>s</code> represents a valid expression.</li>
+	<li>Every number and running calculation will fit in a signed 32-bit integer.</li>
 </ul>
 
 ### Related Topics

problems/basic-calculator/README.md

@@ -11,14 +11,14 @@
 
 ## [1018. Binary Prefix Divisible By 5 (Easy)](https://leetcode.com/problems/binary-prefix-divisible-by-5 "可被 5 整除的二进制前缀")
 
-<p>Given an array <code>A</code> of <code>0</code>s and <code>1</code>s, consider <code>N_i</code>: the i-th subarray from <code>A[0]</code> to <code>A[i]</code>&nbsp;interpreted&nbsp;as a binary number (from most-significant-bit to least-significant-bit.)</p>
+<p>Given an array <code>nums</code> of <code>0</code>s and <code>1</code>s, consider <code>x<sub>i</sub></code>: the i-th subarray from <code>nums[0]</code> to <code>nums[i]</code>&nbsp;interpreted&nbsp;as a binary number (from most-significant-bit to least-significant-bit.)</p>
 
-<p>Return a list of booleans&nbsp;<code>answer</code>, where <code>answer[i]</code> is <code>true</code>&nbsp;if and only if <code>N_i</code>&nbsp;is divisible by 5.</p>
+<p>Return a list of booleans&nbsp;<code>answer</code>, where <code>answer[i]</code> is <code>true</code>&nbsp;if and only if <code>x<sub>i</sub></code>&nbsp;is divisible by 5.</p>
 
 <p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Input: </strong><span id="example-input-1-1">[0,1,1]</span>
+<strong>Input: </strong>nums = <span id="example-input-1-1">[0,1,1]</span>
 <strong>Output: </strong><span id="example-output-1">[true,false,false]</span>
 <strong>Explanation: </strong>
 The input numbers in binary are 0, 01, 011; which are 0, 1, and 3 in base-10.  Only the first number is divisible by 5, so answer[0] is true.
@@ -27,21 +27,21 @@ The input numbers in binary are 0, 01, 011; which are 0, 1, and 3 in base-10.  O
 <p><strong>Example 2:</strong></p>
 
 <pre>
-<strong>Input: </strong><span id="example-input-2-1">[1,1,1]</span>
+<strong>Input: </strong>nums = <span id="example-input-2-1">[1,1,1]</span>
 <strong>Output: </strong><span id="example-output-2">[false,false,false]</span>
 </pre>
 
 <p><strong>Example 3:</strong></p>
 
 <pre>
-<strong>Input: </strong><span id="example-input-3-1">[0,1,1,1,1,1]</span>
+<strong>Input: </strong>nums = <span id="example-input-3-1">[0,1,1,1,1,1]</span>
 <strong>Output: </strong><span id="example-output-3">[true,false,false,false,true,false]</span>
 </pre>
 
 <p><strong>Example 4:</strong></p>
 
 <pre>
-<strong>Input: </strong><span id="example-input-4-1">[1,1,1,0,1]</span>
+<strong>Input: </strong>nums = <span id="example-input-4-1">[1,1,1,0,1]</span>
 <strong>Output: </strong><span id="example-output-4">[false,false,false,false,false]</span>
 </pre>
 
@@ -50,8 +50,8 @@ The input numbers in binary are 0, 01, 011; which are 0, 1, and 3 in base-10.  O
 <p><strong>Note:</strong></p>
 
 <ol>
-	<li><code>1 &lt;= A.length &lt;= 30000</code></li>
-	<li><code>A[i]</code> is <code>0</code> or <code>1</code></li>
+	<li><code>1 &lt;= nums.length &lt;= 30000</code></li>
+	<li><code>nums[i]</code> is <code>0</code> or <code>1</code></li>
 </ol>
 
 ### Related Topics

problems/binary-prefix-divisible-by-5/README.md

@@ -13,6 +13,8 @@
 
 <p>Given an array of integers <code>nums</code> which is sorted in ascending order, and an integer <code>target</code>, write a function to search <code>target</code> in <code>nums</code>. If <code>target</code> exists, then return its index. Otherwise, return <code>-1</code>.</p>
 
+<p>You must&nbsp;write an algorithm with&nbsp;<code>O(log n)</code>&nbsp;runtime complexity.</p>
+
 <p>&nbsp;</p>
 <p><strong>Example 1:</strong></p>
 

problems/binary-search/README.md

@@ -11,21 +11,21 @@
 
 ## [1016. Binary String With Substrings Representing 1 To N (Medium)](https://leetcode.com/problems/binary-string-with-substrings-representing-1-to-n "子串能表示从 1 到 N 数字的二进制串")
 
-<p>Given a binary string <code>S</code> (a string consisting only of &#39;0&#39; and &#39;1&#39;s) and a positive integer <code>N</code>, return true if and only if for every integer X from 1 to N, the binary representation of X is a substring of S.</p>
+<p>Given a binary string <code>s</code> (a string consisting only of &#39;0&#39; and &#39;1&#39;s) and a positive integer <code>n</code>, return true if and only if for every integer <code>x</code> from <code>1</code> to <code>n</code>, the binary representation of <code>x</code> is a substring of <code>s</code>.</p>
 
 <p>&nbsp;</p>
 
 <p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Input: </strong>S = <span id="example-input-1-1">&quot;0110&quot;</span>, N = <span id="example-input-1-2">3</span>
+<strong>Input: </strong>s = <span id="example-input-1-1">&quot;0110&quot;</span>, n = <span id="example-input-1-2">3</span>
 <strong>Output: </strong><span id="example-output-1">true</span>
 </pre>
 
 <p><strong>Example 2:</strong></p>
 
 <pre>
-<strong>Input: </strong>S = <span id="example-input-2-1">&quot;0110&quot;</span>, N = <span id="example-input-2-2">4</span>
+<strong>Input: </strong>s = <span id="example-input-2-1">&quot;0110&quot;</span>, n = <span id="example-input-2-2">4</span>
 <strong>Output: </strong><span id="example-output-2">false</span>
 </pre>
 
@@ -34,8 +34,8 @@
 <p><strong>Note:</strong></p>
 
 <ol>
-	<li><code>1 &lt;= S.length &lt;= 1000</code></li>
-	<li><code>1 &lt;= N &lt;= 10^9</code></li>
+	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
+	<li><code>1 &lt;= n &lt;= 10<sup>9</sup></code></li>
 </ol>
 
 ### Related Topics

problems/binary-string-with-substrings-representing-1-to-n/README.md

@@ -11,32 +11,38 @@
 
 ## [930. Binary Subarrays With Sum (Medium)](https://leetcode.com/problems/binary-subarrays-with-sum "和相同的二元子数组")
 
-<p>In an array <code>nums</code> of <code>0</code>s and <code>1</code>s, how many <strong>non-empty</strong> subarrays have sum <code>goal</code>?</p>
+<p>Given a binary array <code>nums</code> and an integer <code>goal</code>, return <em>the number of non-empty <strong>subarrays</strong> with a sum</em> <code>goal</code>.</p>
 
-<p>&nbsp;</p>
+<p>A <strong>subarray</strong> is a contiguous part of the array.</p>
 
+<p>&nbsp;</p>
 <p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Input: </strong>nums = <span id="example-input-1-1">[1,0,1,0,1]</span>, goal = <span id="example-input-1-2">2</span>
-<strong>Output: </strong><span id="example-output-1">4</span>
-<strong>Explanation: </strong>
-The 4 subarrays are bolded below:
-[<strong>1,0,1</strong>,0,1]
-[<strong>1,0,1,0</strong>,1]
-[1,<strong>0,1,0,1</strong>]
-[1,0,<strong>1,0,1</strong>]
+<strong>Input:</strong> nums = [1,0,1,0,1], goal = 2
+<strong>Output:</strong> 4
+<strong>Explanation:</strong> The 4 subarrays are bolded and underlined below:
+[<u><strong>1,0,1</strong></u>,0,1]
+[<u><strong>1,0,1,0</strong></u>,1]
+[1,<u><strong>0,1,0,1</strong></u>]
+[1,0,<u><strong>1,0,1</strong></u>]
 </pre>
 
-<p>&nbsp;</p>
+<p><strong>Example 2:</strong></p>
 
-<p><strong>Note:</strong></p>
+<pre>
+<strong>Input:</strong> nums = [0,0,0,0,0], goal = 0
+<strong>Output:</strong> 15
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
 
-<ol>
-	<li><code>nums.length &lt;= 30000</code></li>
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 3 * 10<sup>4</sup></code></li>
+	<li><code>nums[i]</code> is either <code>0</code> or <code>1</code>.</li>
 	<li><code>0 &lt;= goal &lt;= nums.length</code></li>
-	<li><code>nums[i]</code>&nbsp;is either <code>0</code>&nbsp;or <code>1</code>.</li>
-</ol>
+</ul>
 
 ### Related Topics
   [[Hash Table](../../tag/hash-table/README.md)]