3247. Number of Subsequences with Odd Sum

Given an array nums, return the number of subsequences with an odd sum of elements.

Since the answer may be very large, return it modulo 109 + 7.

3284. Sum of Consecutive Subarrays

We call an array arr of length n consecutive if one of the following holds:

• arr[i] - arr[i - 1] == 1 for all 1 <= i < n.
• arr[i] - arr[i - 1] == -1 for all 1 <= i < n.

The value of an array is the sum of its elements.

For example, [3, 4, 5] is a consecutive array of value 12 and [9, 8] is another of value 17. While [3, 4, 3] and [8, 6] are not consecutive.

Given an array of integers nums, return the sum of the values of all consecutive subarrays.

Since the answer may be very large, return it modulo 109 + 7.

Note that an array of length 1 is also considered consecutive.

3231. Minimum Number of Increasing Subsequence to Be Removed

Given an array of integers nums, you are allowed to perform the following operation any number of times:

• Remove a strictly increasing subsequence from the array.

Your task is to find the minimum number of operations required to make the array empty.

3313. Find the Last Marked Nodes in Tree

There exists an undirected tree with n nodes numbered 0 to n - 1. You are given a 2D integer array edges of length n - 1, where edges[i] = [ui, vi] indicates that there is an edge between nodes ui and vi in the tree.

Initially, all nodes are unmarked. After every second, you mark all unmarked nodes which have at least one marked node adjacent to them.

Return an array nodes where nodes[i] is the last node to get marked in the tree, if you mark node i at time t = 0. If nodes[i] has multiple answers for any node i, you can choose any one answer.

3329. Count Substrings With K-Frequency Characters II

Given a string s and an integer k, return the total number of substrings of s where at least one character appears at least k times.

3369. Design an Array Statistics Tracker

Design a data structure that keeps track of the values in it and answers some queries regarding their mean, median, and mode.

Implement the StatisticsTracker class.

• StatisticsTracker(): Initialize the StatisticsTracker object with an empty array.
• void addNumber(int number): Add number to the data structure.
• void removeFirstAddedNumber(): Remove the earliest added number from the data structure.
• int getMean(): Return the floored mean of the numbers in the data structure.
• int getMedian(): Return the median of the numbers in the data structure.
• int getMode(): Return the mode of the numbers in the data structure. If there are multiple modes, return the smallest one.

Note:

• The mean of an array is the sum of all the values divided by the number of values in the array.
• The median of an array is the middle element of the array when it is sorted in non-decreasing order. If there are two choices for a median, the larger of the two values is taken.
• The mode of an array is the element that appears most often in the array.

3383. Minimum Runes to Add to Cast Spell

Alice has just graduated from wizard school, and wishes to cast a magic spell to celebrate. The magic spell contains certain focus points where magic needs to be concentrated, and some of these focus points contain magic crystals which serve as the spell’s energy source. Focus points can be linked through directed runes, which channel magic flow from one focus point to another.

You are given a integer n denoting the number of focus points and an array of integers crystals where crystals[i] indicates a focus point which holds a magic crystal. You are also given two integer arrays flowFrom and flowTo, which represent the existing directed runes. The ith rune allows magic to freely flow from focus point flowFrom[i] to focus point flowTo[i].

You need to find the number of directed runes Alice must add to her spell, such that each focus point either:

• Contains a magic crystal.
• Receives magic flow from another focus point.

Return the minimum number of directed runes that she should add.

3385. Minimum Time to Break Locks II

Bob is stuck in a dungeon and must break n locks, each requiring some amount of energy to break. The required energy for each lock is stored in an array called strength where strength[i] indicates the energy needed to break the ith lock.

To break a lock, Bob uses a sword with the following characteristics:

• The initial energy of the sword is 0.
• The initial factor X by which the energy of the sword increases is 1.
• Every minute, the energy of the sword increases by the current factor X.
• To break the ith lock, the energy of the sword must reach at least strength[i].
• After breaking a lock, the energy of the sword resets to 0, and the factor X increases by 1.

Your task is to determine the minimum time in minutes required for Bob to break all n locks and escape the dungeon.

Return the minimum time required for Bob to break all n locks.

3406. Find the Lexicographically Largest String From the Box II

You are given a string word, and an integer numFriends.

Alice is organizing a game for her numFriends friends. There are multiple rounds in the game, where in each round:

• word is split into numFriends non-empty strings, such that no previous round has had the exact same split.
• All the split words are put into a box.

Find the lexicographically largest string from the box after all the rounds are finished.

A string a is lexicographically smaller than a string b if in the first position where a and b differ, string a has a letter that appears earlier in the alphabet than the corresponding letter in b.
If the first min(a.length, b.length) characters do not differ, then the shorter string is the lexicographically smaller one.

3735. Lexicographically Smallest String After Reverse II

You are given a string s of length n consisting of lowercase English letters.

You must perform exactly one operation by choosing any integer k such that 1 <= k <= n and either:

• reverse the first k characters of s, or
• reverse the last k characters of s.

Return the lexicographically smallest string that can be obtained after exactly one such operation.