3154. Find Number of Ways to Reach the K-th Stair

You are given a non-negative integer k. There exists a staircase with an infinite number of stairs, with the lowest stair numbered 0.

Alice has an integer jump, with an initial value of 0. She starts on stair 1 and wants to reach stair k using any number of operations. If she is on stair i, in one operation she can:

• Go down to stair i - 1. This operation cannot be used consecutively or on stair 0.
• Go up to stair i + 2jump. And then, jump becomes jump + 1.

Return the total number of ways Alice can reach stair k.

Note that it is possible that Alice reaches the stair k, and performs some operations to reach the stair k again.

3153. Sum of Digit Differences of All Pairs

You are given an array nums consisting of positive integers where all integers have the same number of digits.

The digit difference between two integers is the count of different digits that are in the same position in the two integers.

Return the sum of the digit differences between all pairs of integers in nums.

3152. Special Array II

An array is considered special if every pair of its adjacent elements contains two numbers with different parity.

You are given an array of integer nums and a 2D integer matrix queries, where for queries[i] = [fromi, toi] your task is to check that subarray nums[fromi..toi] is special or not.

Return an array of booleans answer such that answer[i] is true if nums[fromi..toi] is special.

3151. Special Array I

An array is considered special if every pair of its adjacent elements contains two numbers with different parity.

You are given an array of integers nums. Return true if nums is a special array, otherwise, return false.

1742. Maximum Number of Balls in a Box

You are working in a ball factory where you have n balls numbered from lowLimit up to highLimit inclusive (i.e., n == highLimit - lowLimit + 1), and an infinite number of boxes numbered from 1 to infinity.

Your job at this factory is to put each ball in the box with a number equal to the sum of digits of the ball’s number. For example, the ball number 321 will be put in the box number 3 + 2 + 1 = 6 and the ball number 10 will be put in the box number 1 + 0 = 1.

Given two integers lowLimit and highLimit, return the number of balls in the box with the most balls.

1550. Three Consecutive Odds

Given an integer array arr, return true if there are three consecutive odd numbers in the array. Otherwise, return false.

2423. Remove Letter To Equalize Frequency

You are given a 0-indexed string word, consisting of lowercase English letters. You need to select one index and remove the letter at that index from word so that the frequency of every letter present in word is equal.

Return true if it is possible to remove one letter so that the frequency of all letters in word are equal, and false otherwise.

Note:

• The frequency of a letter x is the number of times it occurs in the string.
• You must remove exactly one letter and cannot choose to do nothing.

3151. Maximum Number of Upgradable Servers

You have n data centers and need to upgrade their servers.

You are given four arrays count, upgrade, sell, and money of length n, which show:

• The number of servers
• The cost of upgrading a single server
• The money you get by selling a server
• The money you initially have

for each data center respectively.

Return an array answer, where for each data center, the corresponding element in answer represents the maximum number of servers that can be upgraded.

Note that the money from one data center cannot be used for another data center.

1708. Largest Subarray Length K

An array A is larger than some array B if for the first index i where A[i] != B[i], A[i] > B[i].

For example, consider 0-indexing:

• [1,3,2,4] > [1,2,2,4], since at index 1, 3 > 2.
• [1,4,4,4] < [2,1,1,1], since at index 0, 1 < 2.

A subarray is a contiguous subsequence of the array.

Given an integer array nums of distinct integers, return the largest subarray of nums of length k.

1826. Faulty Sensor

sensor1 and sensor2, where sensor1[i] and sensor2[i] are the ith data points collected by the two sensors.

However, this type of sensor has a chance of being defective, which causes exactly one data point to be dropped. After the data is dropped, all the data points to the right of the dropped data are shifted one place to the left, and the last data point is replaced with some random value. It is guaranteed that this random value will not be equal to the dropped value.

• For example, if the correct data is [1,2,**3**,4,5] and 3 is dropped, the sensor could return [1,2,4,5,**7**]``7).

1 or 2) with the defect. If there is no defect in either sensor or if it is impossible to determine the defective sensor, return -1.