Update: description

problems/evaluate-division/README.md

@@ -11,25 +11,25 @@
 
 ## 399. Evaluate Division (Medium)
 
-<p>
-Equations are given in the format <code>A / B = k</code>, where  <code>A</code> and <code>B</code> are variables represented as strings, and <code>k</code> is a real number (floating point number). Given some queries, return the answers. If the answer does not exist, return <code>-1.0</code>.
-</p>
-<p><b>Example:</b><br/>
-Given <code> a / b = 2.0, b / c = 3.0.</code> <br/>queries are: <code> a / c = ?,  b / a = ?, a / e = ?,  a / a = ?, x / x = ? .</code> <br/>return <code> [6.0, 0.5, -1.0, 1.0, -1.0 ].</code>
-</p>
-<p>
-The input is: <code> vector&lt;pair&lt;string, string&gt;&gt; equations, vector&lt;double&gt;&amp; values, vector&lt;pair&lt;string, string&gt;&gt; queries </code>, where <code>equations.size() == values.size()</code>, and the values are positive. This represents the equations. Return <code> vector&lt;double&gt;</code>.
-</p>
-
-<p>According to the example above:
-<pre>equations = [ ["a", "b"], ["b", "c"] ],
+<p>Equations are given in the format <code>A / B = k</code>, where <code>A</code> and <code>B</code> are variables represented as strings, and <code>k</code> is a real number (floating point number). Given some queries, return the answers. If the answer does not exist, return <code>-1.0</code>.</p>
+
+<p><b>Example:</b><br />
+Given <code> a / b = 2.0, b / c = 3.0.</code><br />
+queries are: <code> a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ? .</code><br />
+return <code> [6.0, 0.5, -1.0, 1.0, -1.0 ].</code></p>
+
+<p>The input is: <code> vector&lt;pair&lt;string, string&gt;&gt; equations, vector&lt;double&gt;&amp; values, vector&lt;pair&lt;string, string&gt;&gt; queries </code>, where <code>equations.size() == values.size()</code>, and the values are positive. This represents the equations. Return <code> vector&lt;double&gt;</code>.</p>
+
+<p>According to the example above:</p>
+
+<pre>
+equations = [ [&quot;a&quot;, &quot;b&quot;], [&quot;b&quot;, &quot;c&quot;] ],
 values = [2.0, 3.0],
-queries = [ ["a", "c"], ["b", "a"], ["a", "e"], ["a", "a"], ["x", "x"] ]. </pre>
-</p>
+queries = [ [&quot;a&quot;, &quot;c&quot;], [&quot;b&quot;, &quot;a&quot;], [&quot;a&quot;, &quot;e&quot;], [&quot;a&quot;, &quot;a&quot;], [&quot;x&quot;, &quot;x&quot;] ]. </pre>
+
+<p>&nbsp;</p>
 
-<p>
-The input is always valid. You may assume that evaluating the queries will result in no division by zero and there is no contradiction.
-</p>
+<p>The input is always valid. You may assume that evaluating the queries will result in no division by zero and there is no contradiction.</p>
 
 ### Related Topics
   [[Union Find](https://github.com/openset/leetcode/tree/master/tag/union-find/README.md)]

problems/perfect-rectangle/README.md

@@ -89,3 +89,6 @@ Return false. Because two of the rectangles overlap with each other.
 </pre>
 
 <p>&nbsp;</p>
+
+### Related Topics
+  [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)]

problems/rectangle-area-ii/README.md

@@ -44,3 +44,4 @@
 
 ### Related Topics
   [[Segment Tree](https://github.com/openset/leetcode/tree/master/tag/segment-tree/README.md)]
+  [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)]

problems/single-element-in-a-sorted-array/README.md

@@ -11,24 +11,24 @@
 
 ## 540. Single Element in a Sorted Array (Medium)
 
-<p>
-Given a sorted array consisting of only integers where every element appears twice except for one element which appears once. Find this single element that appears only once. 
-</p>
+<p>Given a sorted array consisting of only integers where every element appears exactly twice except for one element which appears exactly&nbsp;once. Find this single element that appears only once.</p>
+
+<p>&nbsp;</p>
+
+<p><b>Example 1:</b></p>
 
-<p><b>Example 1:</b><br />
 <pre>
 <b>Input:</b> [1,1,2,3,3,4,4,8,8]
 <b>Output:</b> 2
 </pre>
-</p>
 
-<p><b>Example 2:</b><br />
+<p><b>Example 2:</b></p>
+
 <pre>
 <b>Input:</b> [3,3,7,7,10,11,11]
 <b>Output:</b> 10
 </pre>
-</p>
 
-<p><b>Note:</b>
-Your solution should run in O(log n) time and O(1) space.
-</p>
+<p>&nbsp;</p>
+
+<p><b>Note:</b> Your solution should run in O(log n) time and O(1) space.</p>

problems/symmetric-tree/README.md

@@ -13,31 +13,32 @@
 
 <p>Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).</p>
 
-<p>
-For example, this binary tree <code>[1,2,2,3,4,4,3]</code> is symmetric:
+<p>For example, this binary tree <code>[1,2,2,3,4,4,3]</code> is symmetric:</p>
+
 <pre>
     1
    / \
   2   2
  / \ / \
 3  4 4  3
 </pre>
-</p>
-<p>
-But the following <code>[1,2,2,null,3,null,3]</code>  is not:<br />
+
+<p>&nbsp;</p>
+
+<p>But the following <code>[1,2,2,null,3,null,3]</code> is not:</p>
+
 <pre>
     1
    / \
   2   2
    \   \
    3    3
 </pre>
-</p>
 
-<p>
-<b>Note:</b><br />
-Bonus points if you could solve it both recursively and iteratively.
-</p>
+<p>&nbsp;</p>
+
+<p><b>Note:</b><br />
+Bonus points if you could solve it both recursively and iteratively.</p>
 
 ### Related Topics
   [[Tree](https://github.com/openset/leetcode/tree/master/tag/tree/README.md)]

problems/the-skyline-problem/README.md

@@ -36,6 +36,7 @@
   [[Binary Indexed Tree](https://github.com/openset/leetcode/tree/master/tag/binary-indexed-tree/README.md)]
   [[Segment Tree](https://github.com/openset/leetcode/tree/master/tag/segment-tree/README.md)]
   [[Divide and Conquer](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)]
+  [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)]
 
 ### Similar Questions
   1. [Falling Squares](https://github.com/openset/leetcode/tree/master/problems/falling-squares) (Hard)

problems/validate-binary-search-tree/README.md

@@ -21,13 +21,16 @@
 	<li>Both the left and right subtrees must also be binary search trees.</li>
 </ul>
 
+<p>&nbsp;</p>
+
 <p><strong>Example 1:</strong></p>
 
 <pre>
-<strong>Input:</strong>
     2
    / \
   1   3
+
+<strong>Input:</strong>&nbsp;[2,1,3]
 <strong>Output:</strong> true
 </pre>
 
@@ -39,9 +42,10 @@
   1   4
 &nbsp;    / \
 &nbsp;   3   6
+
+<strong>Input:</strong> [5,1,4,null,null,3,6]
 <strong>Output:</strong> false
-<strong>Explanation:</strong> The input is: [5,1,4,null,null,3,6]. The root node&#39;s value
-&nbsp;            is 5 but its right child&#39;s value is 4.
+<strong>Explanation:</strong> The root node&#39;s value is 5 but its right child&#39;s value is 4.
 </pre>
 
 ### Related Topics