Given an integer array called nums and an integer called target, return the number of triplets that exist in the array such that nums[i] + nums[j] + nums[k] &lt; target where 0 &lt;= i &lt; j &lt; k &lt; len(nums).
Example:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: nums = <code>[-2,0,1,3]</code>, target = 2 Output: 2 Explanation:&nbsp;These are the two triplets that are less than 2: &nbsp; [-2,0,1] [-2,0,3]</pre>
&nbsp;

Triplet Sum

Given an array of integers, A, and a target integer, find the number of tuples consisting of 3 elements: i, j, k such that i &lt; j &lt; k and A[i] + A[j] + A[k] == target.
Return the result as modulo&nbsp;<code>10^9 + 7&nbsp;</code>since the answer can be large.&nbsp;
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [1,1,2,2,3,3,4,4,5,5], target = 8
Output: 20
Explanation: 

This tuple set, (1, 2, 5), shows up 8 times; This tuple set, (1, 3, 4), shows up 8 times; This tuple set, (2, 2, 4), shows up 2 times; This tuple set, (2, 3, 3), shows up 2 times.</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [1,1,2,2,2,2], target = 5
Output: 12
Explanation: 
A[i] = 1, A[j] = A[k] = 2 occurs 12 times:
We select one 1 from [1,1] in 2 ways,
and select two different 2s from [2,2,2,2] in 6 ways.
</pre>
</div>

3sum Multiplicity

Given an array <code>nums</code> of n integers, are there elements a, b, c in <code>nums</code> such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Given an array of integers, return the index of all 3 distinct elements: x, y, z such that x + y + z = 0. Don't return duplicates.
&nbsp;
Example:
<pre style="white-space: pre-wrap; word-break: keep-all;">Given nums = [-1, 0, 1, 2, -1, -4],
</pre>

<pre style="white-space: pre-wrap; word-break: keep-all;">
A solution set is:
[
 [-1, 0, 1],
 [-1, -1, 2]
]
</pre>

3sum

Given an array containing only 0s and 1s and an integer S, return the number of non-empty subarrays that sum up to S.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [1,0,1,0,1], S = 2
Output: 4
Explanation: 
These are the 4 subarrays:
[1,0,1,0,1]
[1,0,1,0,1]
[1,0,1,0,1]
[1,0,1,0,1]
</pre>
&nbsp;

Binary Subarray Sums

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

&nbsp;
You are given an array of non-negative integers and each integer represents the height of vertical lines on the x-axis, at the corresponding index number. Find the maximum area of water that any given two vertical lines can hold.&nbsp;
&nbsp;
Note: There are at least two vertical lines&nbsp;
&nbsp;
<img style="width: 600px; height: 287px;" src="https://s3-lc-upload.s3.amazonaws.com/uploads/2018/07/17/question_11.jpg" alt="" />
The above graph represents the array&nbsp;[1,8,6,2,5,4,8,3,7]. In this case, the blue area represents the maximum area of water, which is 49.&nbsp;
&nbsp;
Example:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,8,6,2,5,4,8,3,7]
Output: 49 Input: [3,5,3,2,1,9,3,8] Output: 30</pre>

Largest Container With Water

You are given an array of integers and are asked to find and return the duplicate number in the array. Only one number is repeated in the array.
Note:
Your solution must have a complexity that's less than O(n2). Your solution's space complexity should be constant O(1). You are not allowed to modify the input array. Only one value is repeated in the input array but it can be repeated multiple times.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: <code>[1,3,4,2,2]</code> Output: 2</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [3,1,3,4,2]
Output: 3</pre>
&nbsp;

Identify Repeated Number

Given an array of integers, tree, that represent a row of trees, each i'th tree produces fruit with type tree[i].
You have two baskets and each basket can hold any quantity of fruit but each basket can only contain one type of fruit.
Follow this procedure: begin at any tree&nbsp;of your choice, then continuously perform the following steps:
<ol>
<li>Add one piece of fruit from this tree to one of your baskets.&nbsp; If you cannot, stop.</li>
<li>Move to the tree on the right of the current tree.&nbsp; If there is no tree to the right, stop.</li>
</ol>
After you pick a beginning tree, you must keep performing step 1 followed by step 2 until you have to stop.
Return the total amount of fruit you can collect with this procedure.
&nbsp;
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,2,1]
Output: 3
Explanation: We can collect a fruit from each of these trees into our 2 baskets: [1,2,1].
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [0,1,2,2]
Output: 3
Explanation: We can collect a fruit from each of these trees into our 2 baskets: [1,2,2].
If we started at the first tree, we would only be able to collect from these trees: [0, 1].
</pre>
<div>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,2,3,2,2]
Output: 4
Explanation: We can collect a fruit from each of these trees into our 2 baskets: [2,3,2,2]. If we started at the first tree, we would only be able to collect from these trees: [1, 2].
</pre>
<div>
Example 4:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [3,3,3,1,2,1,1,2,3,3,4]
Output: 5
Explanation: We can collect a fruit from each of these trees into our 2 baskets: [1,2,1,1,2].
If we started at the first tree or the eighth tree, we would only be able to collect 4 fruits.
</pre>
&nbsp;
</div>
</div>
</div>
Constraints:
<ol>
<li><code>1 &lt;= tree.length &lt;= 40000</code></li>
<li><code>0 &lt;= tree[i] &lt; tree.length</code></li>
</ol>

Maximize Fruits

Given two integer arrays, return the intersection of the two arrays.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]</pre>
</div>
&nbsp;

Intersection Of Two Arrays

You are given two lists of intervals. Each list is sorted and pairwise disjoint. Your task is to return the intersection of the two lists.
<div>
Example 1:
<img style="width: 506px; height: auto;" src="https://swecareers-images.s3.us-east-2.amazonaws.com/images/intersection-of-intervals/example-1.png" alt="" />
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: A = [[0,2],[5,10],[13,23],[24,25]], B = [[1,5],[8,12],[15,24],[25,26]]
Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]
</pre>
</div>

Intersection Of Intervals

Given an array of integers and an integer k, return the number of unique pairs such that their absolute difference is k.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [3, 1, 4, 1, 5], k = 2
Output: 2
Explanation: The 2 k difference pairs are: (1, 3) and (3, 5). The pair (1, 3) is used twice but we don't count it twice since we are only counting unique pairs.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input:[1, 2, 3, 4, 5], k = 1
Output: 4
Explanation: There are 4 k-difference pairs in the array, (1, 2), (2, 3), (3, 4) and (4, 5).
</pre>
Example 3:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1, 3, 1, 5, 4], k = 0
Output: 1
Explanation: There is only 1 k-difference pair in the array, (1, 1).
</pre>
Assume:
<ol>
<li>The pairs (i, j) and (j, i) are counted as one pair.</li>
<li>The length of the array is less than 10,000.</li>
</ol>

K Difference Pairs

Given an array of non-negative integers, X, return the length of the longest&nbsp;mountain. Return <code>0</code> if there is no mountain.
Mountain is defined by the following properties:
<ul>
<li><code>X.length &gt;= 3</code></li>
<li>There exists some <code>0 &lt; i&nbsp;&lt; X.length - 1</code> such that <code>X[0] &lt; X[1] &lt; ... X[i-1] &lt; X[i] &gt; X[i+1] &gt; ... &gt; X[X.length - 1]</code></li>
</ul>
&nbsp;
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [3,2,5,3,2,6,7,4]
Output: 4
Explanation: The largest mountain is [2,5,3,2], with the length 4.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [3,3,3]
Output: 0
Explanation: There is no mountain.
</pre>
Note:
<ol>
<li><code>0 &lt;= X.length &lt;= 10000</code></li>
</ol>
Next Step:
<ul>
<li>Try solving it in one pass</li>
<li>Try solving it in <code>O(1)</code> space</li>
</ul>

Find Longest Mountain

Given a string, return the size of the longest substring such that it contains at most 2 distinct characters.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "eceba"
Output: 3
Explanation: t is "ece" which its size is 3.
</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "ccaabbb"
Output: 5
Explanation: t is "aabbb" which its size is 5.
</pre>

Two Distinct Character Substring

You are given a string, s. Find the length of the longest substring without repeating characters.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "abcabc"
Output: 3 
Explanation: Longest substring is <code>"abc"</code>, with the length of 3.</pre>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "ffewef"
Output: 3
Explanation: Longest substring is <code>"few"</code>, with the length of 3.</pre>
&nbsp;

Maximum Substring With Non Repeating Characters

Given an array with only 1's and 0's return the longest possible number of consecutive 1's in the array if you can only flip one 0 in the array.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [1,0,1,1,0]
Output: 4
Explanation: Flipping the first zero will get the the longest length of consecutive 1s. You are then left with 4 consecutive 1s.
</pre>
&nbsp;

Longest Consecutive Ones II

Given 2 strings called: S and T, return the minimum substring in S that contains all characters of T. Do it in O(n) complexity. If no substring exists then return the empty string. If the substring exists then you are guaranteed to only have one unique solution.
Example:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: S = "ADOBECODEBANC", T = "ABC"
Output: "BANC"
</pre>
&nbsp;

Minimum Full Window

Given a string return the string with all the vowels in reverse order.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "hello"
Output: "holle"
</pre>
<div>
Example 2:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: "swecareers"
Output: "sweceraers"</pre>
</div>
Note: Vowels are: 'a', 'e', 'i', 'o', 'u'. 'y' is not a vowel.
&nbsp;

Vowel Reversal

Given a list of positive integers:&nbsp;<code>nums</code> and integer <code>k</code>, return the number of contiguous subarrays such that the product is strictly less than <code>k</code>.
Example 1:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: nums = [6, 2, 5, 10], k = 100
Output: 8
Explanation: The 8 subarrays that have product less than 100 are: [6], [2], [5], [10], [6, 2], [2, 5], [5, 10], [6, 2, 5]. 
</pre>

Product Subarrays Less Than K

Given an array of non-negative integers that represent elevations in a mountain, return the total amount of water the mountains store after raining.
<img style="width: auto; height: 100px;" src="https://swecareers-images.s3.us-east-2.amazonaws.com/images/water-in-mountains/example-1.png" /> The above mountain is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of water (blue section) are contained.
Example:
<pre style="white-space: pre-wrap; word-break: keep-all;">Input: [0,1,0,2,1,0,1,3,2,1,2,1]
Output: 6</pre>

Water In Mountains

Determine if a given string is a palindrome when ignoring punctuation and cases.

Note:&nbsp;Empty string is a valid palindrome.

Example 1:

<pre style="white-space: pre-wrap; word-break: keep-all;">
Input: &quot;A man, a plan, a canal: Panama&quot;
Output: true
</pre>

Example 2:

<pre style="white-space: pre-wrap; word-break: keep-all;">
Input: &quot;race a car&quot;
Output: false
</pre>

Problem Title	Difficulty	Frequency in Interviews
Water In Mountains	Hard
Maximum Substring With Non Repeating Characters	Medium
3sum	Medium
Minimum Full Window	Hard
Largest Container With Water	Medium
Maximize Fruits	Medium
Intersection Of Intervals	Medium
3sum Multiplicity	Medium
Correct Palindome	Easy
Intersection Of Two Arrays	Easy
Identify Repeated Number	Medium
Product Subarrays Less Than K	Medium
K Difference Pairs	Easy
Two Distinct Character Substring	Hard
Vowel Reversal	Easy
Find Longest Mountain	Medium
Triplet Sum	Medium
Binary Subarray Sums	Medium
Longest Consecutive Ones II	Medium
Safety Boats	Medium

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