Do it for FUN | SUMFIのBlog

[LeetCode] Longest Unequal Adjacent Groups Subsequence I 2023-10-15|PSLeetCode|Problem Solving-Hash Table

2900. Longest Unequal Adjacent Groups Subsequence I

You are given an integer n, a 0-indexed string array words, and a 0-indexed binary array groups, both arrays having length n.

You need to select the longest subsequence from an array of indices [0, 1, ..., n - 1], such that for the subsequence denoted as [i0, i1, ..., ik - 1] having length k, groups[ij] != groups[ij + 1], for each j where 0 < j + 1 < k.

Return a string array containing the words corresponding to the indices (in order) in the selected subsequence. If there are multiple answers, return any of them.

A subsequence of an array is a new array that is formed from the original array by deleting some (possibly none) of the elements without disturbing the relative positions of the remaining elements.

Note: strings in words may be unequal in length.

[LeetCode] Last Visited Integers 2023-10-15|PSLeetCode|Problem Solving

2899. Last Visited Integers

Given a 0-indexed array of strings words where words[i] is either a positive integer represented as a string or the string "prev".

Start iterating from the beginning of the array; for every "prev" string seen in words, find the last visited integer in words which is defined as follows:

Let k be the number of consecutive "prev" strings seen so far (containing the current string). Let nums be the 0-indexed array of integers seen so far and nums_reverse be the reverse of nums, then the integer at (k - 1)th index of nums_reverse will be the last visited integer for this "prev".

If k is greater than the total visited integers, then the last visited integer will be -1.

Return an integer array containing the last visited integers.

[LeetCode] Count of Sub-Multisets With Bounded Sum 2023-10-15|PSLeetCode|Problem Solving-Dynamic Programming-Combinatorics-Sliding Window-Knapsack-Monotonic Deque

2902. Count of Sub-Multisets With Bounded Sum

You are given a 0-indexed array nums of non-negative integers, and two integers l and r.

Return the count of sub-multisets within nums where the sum of elements in each subset falls within the inclusive range of [l, r].

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

A sub-multiset is an unordered collection of elements of the array in which a given value x can occur 0, 1, ..., occ[x] times, where occ[x] is the number of occurrences of x in the array.

Note that:

Two sub-multisets are the same if sorting both sub-multisets results in identical multisets.

The sum of an empty multiset is 0.