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[LeetCode] Count Zero Request Servers 2023-06-25|PSLeetCode|Sorting-Problem Solving-Hash Table-Offline Query Technique

You are given an integer n denoting the total number of servers and a 2D 0-indexed integer array logs, where logs[i] = [server_id, time] denotes that the server with id server_id received a request at time time.

You are also given an integer x and a 0-indexed integer array queries.

Return a 0-indexed integer array arr of length queries.length where arr[i] represents the number of servers that did not receive any requests during the time interval [queries[i] - x, queries[i]].

Note that the time intervals are inclusive.

[LeetCode] Decremental String Concatenation 2023-06-25|PSLeetCode|Problem Solving-Dynamic Programming

2746. Decremental String Concatenation

You are given a 0-indexed array words containing n strings.

Let’s define a join operation join(x, y) between two strings x and y as concatenating them into xy. However, if the last character of x is equal to the first character of y, one of them is deleted.

For example join("ab", "ba") = "aba" and join("ab", "cde") = "abcde".

You are to perform n - 1 join operations. Let str0 = words[0]. Starting from i = 1 up to i = n - 1, for the ith operation, you can do one of the following:

Make stri = join(stri - 1, words[i])

Make stri = join(words[i], stri - 1)

Your task is to minimize the length of strn - 1.

Return an integer denoting the minimum possible length of strn - 1.

[LeetCode] Construct the Longest New String 2023-06-25|PSLeetCode|Problem Solving-Greedy

2745. Construct the Longest New String

You are given three integers x, y, and z.

You have x strings equal to "AA", y strings equal to "BB", and z strings equal to "AB". You want to choose some (possibly all or none) of these strings and concactenate them in some order to form a new string. This new string must not contain "AAA" or "BBB" as a substring.

Return the maximum possible length of the new string.

A substring is a contiguous non-empty sequence of characters within a string.

[LeetCode] Find Maximum Number of String Pairs 2023-06-25|PSLeetCode|Problem Solving-Hash Table

2744. Find Maximum Number of String Pairs

You are given a 0-indexed array words consisting of distinct strings.

The string words[i] can be paired with the string words[j] if:

The string words[i] is equal to the reversed string of words[j].

0 <= i < j < words.length.

Return the maximum number of pairs that can be formed from the array words.

Note that each string can belong in at most one pair.