update

leetcode/problem/find-the-original-array-of-prefix-xor.html

@@ -0,0 +1,39 @@
+<p>You are given an <strong>integer</strong> array <code>pref</code> of size <code>n</code>. Find and return <em>the array </em><code>arr</code><em> of size </em><code>n</code><em> that satisfies</em>:</p>
+
+<ul>
+	<li><code>pref[i] = arr[0] ^ arr[1] ^ ... ^ arr[i]</code>.</li>
+</ul>
+
+<p>Note that <code>^</code> denotes the <strong>bitwise-xor</strong> operation.</p>
+
+<p>It can be proven that the answer is <strong>unique</strong>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> pref = [5,2,0,3,1]
+<strong>Output:</strong> [5,7,2,3,2]
+<strong>Explanation:</strong> From the array [5,7,2,3,2] we have the following:
+- pref[0] = 5.
+- pref[1] = 5 ^ 7 = 2.
+- pref[2] = 5 ^ 7 ^ 2 = 0.
+- pref[3] = 5 ^ 7 ^ 2 ^ 3 = 3.
+- pref[4] = 5 ^ 7 ^ 2 ^ 3 ^ 2 = 1.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> pref = [13]
+<strong>Output:</strong> [13]
+<strong>Explanation:</strong> We have pref[0] = arr[0] = 13.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= pref.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>0 &lt;= pref[i] &lt;= 10<sup>6</sup></code></li>
+</ul>

leetcode/problem/paths-in-matrix-whose-sum-is-divisible-by-k.html

@@ -0,0 +1,42 @@
+<p>You are given a <strong>0-indexed</strong> <code>m x n</code> integer matrix <code>grid</code> and an integer <code>k</code>. You are currently at position <code>(0, 0)</code> and you want to reach position <code>(m - 1, n - 1)</code> moving only <strong>down</strong> or <strong>right</strong>.</p>
+
+<p>Return<em> the number of paths where the sum of the elements on the path is divisible by </em><code>k</code>. Since the answer may be very large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/08/13/image-20220813183124-1.png" style="width: 437px; height: 200px;" />
+<pre>
+<strong>Input:</strong> grid = [[5,2,4],[3,0,5],[0,7,2]], k = 3
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> There are two paths where the sum of the elements on the path is divisible by k.
+The first path highlighted in red has a sum of 5 + 2 + 4 + 5 + 2 = 18 which is divisible by 3.
+The second path highlighted in blue has a sum of 5 + 3 + 0 + 5 + 2 = 15 which is divisible by 3.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/08/17/image-20220817112930-3.png" style="height: 85px; width: 132px;" />
+<pre>
+<strong>Input:</strong> grid = [[0,0]], k = 5
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> The path highlighted in red has a sum of 0 + 0 = 0 which is divisible by 5.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+<img src="https://assets.leetcode.com/uploads/2022/08/12/image-20220812224605-3.png" style="width: 257px; height: 200px;" />
+<pre>
+<strong>Input:</strong> grid = [[7,3,4,9],[2,3,6,2],[2,3,7,0]], k = 1
+<strong>Output:</strong> 10
+<strong>Explanation:</strong> Every integer is divisible by 1 so the sum of the elements on every possible path is divisible by k.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>m == grid.length</code></li>
+	<li><code>n == grid[i].length</code></li>
+	<li><code>1 &lt;= m, n &lt;= 5 * 10<sup>4</sup></code></li>
+	<li><code>1 &lt;= m * n &lt;= 5 * 10<sup>4</sup></code></li>
+	<li><code>0 &lt;= grid[i][j] &lt;= 100</code></li>
+	<li><code>1 &lt;= k &lt;= 50</code></li>
+</ul>

leetcode/problem/the-employee-that-worked-on-the-longest-task.html

@@ -0,0 +1,63 @@
+<p>There are <code>n</code> employees, each with a unique id from <code>0</code> to <code>n - 1</code>.</p>
+
+<p>You are given a 2D integer array <code>logs</code> where <code>logs[i] = [id<sub>i</sub>, leaveTime<sub>i</sub>]</code> where:</p>
+
+<ul>
+	<li><code>id<sub>i</sub></code> is the id of the employee that worked on the <code>i<sup>th</sup></code> task, and</li>
+	<li><code>leaveTime<sub>i</sub></code> is the time at which the employee finished the <code>i<sup>th</sup></code> task. All the values <code>leaveTime<sub>i</sub></code> are <strong>unique</strong>.</li>
+</ul>
+
+<p>Note that the <code>i<sup>th</sup></code> task starts the moment right after the <code>(i - 1)<sup>th</sup></code> task ends, and the <code>0<sup>th</sup></code> task starts at time <code>0</code>.</p>
+
+<p>Return <em>the id of the employee that worked the task with the longest time.</em> If there is a tie between two or more employees, return<em> the <strong>smallest</strong> id among them</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 10, logs = [[0,3],[2,5],[0,9],[1,15]]
+<strong>Output:</strong> 1
+<strong>Explanation:</strong> 
+Task 0 started at 0 and ended at 3 with 3 units of times.
+Task 1 started at 3 and ended at 5 with 2 units of times.
+Task 2 started at 5 and ended at 9 with 4 units of times.
+Task 3 started at 9 and ended at 15 with 6 units of times.
+The task with the longest time is task 3 and the employee with id 1 is the one that worked on it, so we return 1.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 26, logs = [[1,1],[3,7],[2,12],[7,17]]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> 
+Task 0 started at 0 and ended at 1 with 1 unit of times.
+Task 1 started at 1 and ended at 7 with 6 units of times.
+Task 2 started at 7 and ended at 12 with 5 units of times.
+Task 3 started at 12 and ended at 17 with 5 units of times.
+The tasks with the longest time is task 1. The employees that worked on it is 3, so we return 3.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> n = 2, logs = [[0,10],[1,20]]
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> 
+Task 0 started at 0 and ended at 10 with 10 units of times.
+Task 1 started at 10 and ended at 20 with 10 units of times.
+The tasks with the longest time are tasks 0 and 1. The employees that worked on them are 0 and 1, so we return the smallest id 0.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= n &lt;= 500</code></li>
+	<li><code>1 &lt;= logs.length &lt;= 500</code></li>
+	<li><code>logs[i].length == 2</code></li>
+	<li><code>0 &lt;= id<sub>i</sub> &lt;= n - 1</code></li>
+	<li><code>1 &lt;= leaveTime<sub>i</sub> &lt;= 500</code></li>
+	<li><code>id<sub>i</sub> != id<sub>i+1</sub></code></li>
+	<li><code>leaveTime<sub>i</sub></code> are sorted in a strictly increasing order.</li>
+</ul>

leetcode/problem/using-a-robot-to-print-the-lexicographically-smallest-string.html

@@ -0,0 +1,51 @@
+<p>You are given a string <code>s</code> and a robot that currently holds an empty string <code>t</code>. Apply one of the following operations until <code>s</code> and <code>t</code> <strong>are both empty</strong>:</p>
+
+<ul>
+	<li>Remove the <strong>first</strong> character of a string <code>s</code> and give it to the robot. The robot will append this character to the string <code>t</code>.</li>
+	<li>Remove the <strong>last</strong> character of a string <code>t</code> and give it to the robot. The robot will write this character on paper.</li>
+</ul>
+
+<p>Return <em>the lexicographically smallest string that can be written on the paper.</em></p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;zza&quot;
+<strong>Output:</strong> &quot;azz&quot;
+<strong>Explanation:</strong> Let p denote the written string.
+Initially p=&quot;&quot;, s=&quot;zza&quot;, t=&quot;&quot;.
+Perform first operation three times p=&quot;&quot;, s=&quot;&quot;, t=&quot;zza&quot;.
+Perform second operation three times p=&quot;azz&quot;, s=&quot;&quot;, t=&quot;&quot;.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;bac&quot;
+<strong>Output:</strong> &quot;abc&quot;
+<strong>Explanation:</strong> Let p denote the written string.
+Perform first operation twice p=&quot;&quot;, s=&quot;c&quot;, t=&quot;ba&quot;. 
+Perform second operation twice p=&quot;ab&quot;, s=&quot;c&quot;, t=&quot;&quot;. 
+Perform first operation p=&quot;ab&quot;, s=&quot;&quot;, t=&quot;c&quot;. 
+Perform second operation p=&quot;abc&quot;, s=&quot;&quot;, t=&quot;&quot;.
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> s = &quot;bdda&quot;
+<strong>Output:</strong> &quot;addb&quot;
+<strong>Explanation:</strong> Let p denote the written string.
+Initially p=&quot;&quot;, s=&quot;bdda&quot;, t=&quot;&quot;.
+Perform first operation four times p=&quot;&quot;, s=&quot;&quot;, t=&quot;bdda&quot;.
+Perform second operation four times p=&quot;addb&quot;, s=&quot;&quot;, t=&quot;&quot;.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>s</code> consists of only English lowercase letters.</li>
+</ul>