You have a keyboard that only has these 4 buttons:
<code></code>Button 1: Print an 'A' on the screen
Button 2: Select the whole screen
Button 3: Copy the selected text to buffer
Button 4: Print buffer on the screen and append it to whatever is on the screen.
You are allowed to press the keyboard N times, return the maximum number of 'A's you can print on the screen.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: N = 3
Output: 3
Explanation: 
We can print at most 3 A's on the screen by pressing following buttons: 1, 1, 1
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: N = 7
Output: 9
Explanation: 
We can print at most 9 A's on screen by pressing following buttons:
1, 1, 1, 2, 3, 4, 4
</pre>

Four Button Keyboard

You start off with power P, a score of 0 points and a bag of tokens.
Every token can only be used at most once and each token has a value of token[i] and can be used one of two ways:
1. If we have enough power as token[i], we can play the token face up and lose token[i] power but gain 1 point
2. If we have 1 point, we can play the token face down and gain token[i] power but lose 1 point.
Return the maximum number of points we can have after playing the optimal number of tokens.
<div>
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: tokens = [100], P = 50
Output: 0
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: tokens = [100,200], P = 150
Output: 1
</pre>
<div>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: tokens = [100,200,300,400], P = 200
Output: 2
</pre>
&nbsp;
</div>
</div>
</div>

Token Bag

You have an array, <code>prices</code>, in which the ith element represents the price of stock on day i. 

Find the maximum profit with instructions below: 

<ul>
	<li> You can complete as many transactions as needed. </li>
	<li> You must always sell the stock before you can buy again. You cannot engage in multiple transactions at the same time.
</ul>

Example 1:

<pre style="white-space: pre-wrap; word-break: keep-all;">
Input: [5,2,4,3,10,2]
Output: 9
Explanation: Buy on day 1 (price 2), and sell on day 2 (price 4).
&nbsp; Then buy on day 3 (price 3), and sell on day 4 (price 10). 
&nbsp; maximum profit = (4 - 2) + (10 - 3) = 9.
</pre>

 

Example 2:

<pre style="white-space: pre-wrap; word-break: keep-all;">
Input: [10,9, 8, 7]
Output: 0
Explanation: No transaction is done. maximum profit = 0.</pre>

Maximize Profits In The Stock Market II

Given a list of integers representing people's weight and an integer called limit, return the minimum number of boats to carry every person. A boat can carry at most 2 people as long as the total weight is less than the limit of the boat.
<div>
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: people = [1,2], limit = 3
Output: 1
Explanation: 1 boat (1, 2)
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: people = [3,2,2,1], limit = 3
Output: 3
Explanation: 3 boats (1, 2), (2) and (3)
</pre>
<div>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: people = [3,5,3,4], limit = 5
Output: 4
Explanation: 4 boats (3), (3), (4), (5)</pre>
&nbsp;
</div>
</div>
</div>

Safety Boats

We have a stupid calculator that has a number on its display, we can perform two operations:
- Double: double the number on the screen
- Decrement: subtract 1 from the number on the screen
Given X as the initial number on the screen and a number Y, return the minimum number of operations to get from X to Y.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: X = 2, Y = 3
Output: 2
Explanation: Use the double operation and then use the decrement operation {2 -&gt; 4 -&gt; 3}.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: X = 5, Y = 8
Output: 2
Explanation: Use the decrement operation and then use the double operation {5 -&gt; 4 -&gt; 8}.
</pre>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: X = 3, Y = 10
Output: 3
Explanation: Use the double operation, the decrement operation and then the double operation {3 -&gt; 6 -&gt; 5 -&gt; 10}.
</pre>
Example 4:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: X = 1024, Y = 1
Output: 1023
Explanation: Use decrement operation 1023 times.
</pre>
&nbsp;
Note:
<ol>
<li><code>1 &lt;= X &lt;= 10^9</code></li>
<li><code>1 &lt;= Y &lt;= 10^9</code></li>
</ol>

Stupid Calculator

There are N number of children standing in a line. Each child is assigned a value.
You give candies to each children in the line based on these rules:
<ul>
<li>Each child must get at least one candy.</li>
<li>A child with a higher value gets more candies compared to their neighbors.</li>
</ul>
Return the minimum number of candies you must give out.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,0,2]
Output: 5
Explanation: You can give candies to the first, second and third child with 2, 1, 2 candies respectively.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,2,2]
Output: 4
Explanation: You can give candies to the first, second and third child with 1, 2, 1 candies respectively. The third child gets only 1 candy because it satisfies both the conditions.
</pre>

Give Children Candy

Given an array of integers representing people sitting in a row, return the minimum number of swaps needed such that all couples are sitting next to each other. A swap is considered as any two people in the row standing up and switching seats.
The given array consists of values from 0 to 2N - 1 where N is the number of couples. Couples are paired by the order of numbers. (0, 1) is the first couple, (2, 3) is the second couple etc.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: row = [0, 2, 1, 3]
Output: 1
Explanation: We only need one swap: move the second (row[1]) and third (row[2]) person.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: row = [3, 2, 0, 1]
Output: 0
Explanation: All couples are next to each other so we don't need to swap any people.
</pre>

Hold Hands

Given an array of time intervals that consist of start and end times, return the minimum number of meeting rooms required.
<code>Input: [[s1,e1],[s2,e2],...]</code> (si &lt; ei)
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: <code>[[0, 30],[5, 10],[15, 20]]</code> Output: 2</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [[7,10],[2,4]]
Output: 1</pre>

Meeting Rooms II

You are given a string and are required to remove the duplicate characters in the string such that each character appears once. Return the smallest word that satisfies this condition when arranged in lexicographical order.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: <code>"bcabc"</code> Output: <code>"abc"</code></pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: <code>"cbacdcbc"</code> Output: <code>"acdb"</code></pre>

Delete Repeating Letters

Given a string and check if you can arrange all characters in such a way that no two adjacent characters are the same.
If it is possible, return your result. Otherwise, return an empty string.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: S = "aab"
Output: "aba"
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: S = "aaab"
Output: ""
</pre>
&nbsp;
&nbsp;

Restructure String

Given an array of integers A and another integer K, for each integer in A, we will add a value x to A[i] such that x = -K or x = K.
Once we add the x value to each element in A we have a resulting array, B. Return the smallest possible difference between the max value of B and the min value of B.
<div>
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [1], K = 0
Output: 0
Explanation: B = [1], only one value return 0
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [0,10], K = 2
Output: 6
Explanation: B = [2,8], max - min = 8 - 2 = 6
</pre>
<div>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [1,3,6], K = 3
Output: 3
Explanation: B = [4,6,3], max - min = 6 - 3 = 3
</pre>
&nbsp;
Note:
<ol>
<li><code>1 &lt;= A.length &lt;= 10000</code></li>
<li><code>0 &lt;= A[i] &lt;= 10000</code></li>
<li><code>0 &lt;= K &lt;= 10000</code></li>
</ol>
</div>
</div>
</div>

Problem Title	Difficulty	Frequency in Interviews
Meeting Rooms II	Medium
Restructure String	Medium
Delete Repeating Letters	Hard
Give Children Candy	Hard
Maximize Profits In The Stock Market II	Easy
Hold Hands	Hard
Token Bag	Medium
Stupid Calculator	Medium
Four Button Keyboard	Medium
Safety Boats	Medium
Minimum Range II	Medium

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