Add: Related Topics

Author: openset

problems/distant-barcodes/README.md

@@ -44,3 +44,13 @@ Next >
 <div>
 <div>&nbsp;</div>
 </div>
+
+### Related Topics
+  [[Heap](https://github.com/openset/leetcode/tree/master/tag/heap/README.md)]
+  [[Sort](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+We want to always choose the most common or second most common element to write next.  What data structure allows us to query this effectively?
+</details>

problems/grumpy-bookstore-owner/README.md

@@ -39,3 +39,13 @@ The maximum number of customers that can be satisfied = 1 + 1 + 1 + 1 + 7 + 5 =
 	<li><code>0 &lt;=&nbsp;customers[i] &lt;= 1000</code></li>
 	<li><code>0 &lt;=&nbsp;grumpy[i] &lt;= 1</code></li>
 </ul>
+
+### Related Topics
+  [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+  [[Sliding Window](https://github.com/openset/leetcode/tree/master/tag/sliding-window/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+Say the store owner uses their power in minute 1 to X and we have some answer A.  If they instead use their power from minute 2 to X+1, we only have to use data from minutes 1, 2, X and X+1 to update our answer A.
+</details>

problems/height-checker/README.md

@@ -34,3 +34,12 @@ Students with heights 4, 3 and the last 1 are not standing in the right position
 	<li><code>1 &lt;= heights.length &lt;= 100</code></li>
 	<li><code>1 &lt;= heights[i] &lt;= 100</code></li>
 </ol>
+
+### Related Topics
+  [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+Build the correct order of heights by sorting another array, then compare the two arrays.
+</details>

problems/previous-permutation-with-one-swap/README.md

@@ -20,33 +20,31 @@
 <pre>
 <strong>Input: </strong>[3,2,1]
 <strong>Output: </strong>[3,1,2]
-<strong>Explanation: </strong>
-Swapping 2 and 1.
+<strong>Explanation: </strong>Swapping 2 and 1.
 </pre>
 
 <p><strong>Example 2:</strong></p>
 
 <pre>
 <strong>Input: </strong>[1,1,5]
 <strong>Output: </strong>[1,1,5]
-<strong>Explanation: </strong>
-This is already the smallest permutation.
+<strong>Explanation: </strong>This is already the smallest permutation.
 </pre>
 
 <p><strong>Example 3:</strong></p>
 
 <pre>
 <strong>Input: </strong>[1,9,4,6,7]
 <strong>Output: </strong>[1,7,4,6,9]
-<strong>Explanation: </strong>
-Swapping 9 and 7.
+<strong>Explanation: </strong>Swapping 9 and 7.
 </pre>
 
 <p><strong>Example 4:</strong></p>
 
 <pre>
 <strong>Input: </strong>[3,1,1,3]
-<strong>Output: </strong>[1,1,3,3]
+<strong>Output: </strong>[1,3,1,3]
+<strong>Explanation: </strong>Swapping 1 and 3.
 </pre>
 
 <p>&nbsp;</p>
@@ -57,3 +55,13 @@ Swapping 9 and 7.
 	<li><code>1 &lt;= A.length &lt;= 10000</code></li>
 	<li><code>1 &lt;= A[i] &lt;= 10000</code></li>
 </ol>
+
+### Related Topics
+  [[Greedy](https://github.com/openset/leetcode/tree/master/tag/greedy/README.md)]
+  [[Array](https://github.com/openset/leetcode/tree/master/tag/array/README.md)]
+
+### Hints
+<details>
+<summary>Hint 1</summary>
+You need to swap two values, one larger than the other.  Where is the larger one located?
+</details>