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Longest Alternating Subsequence Gfg, Given an array nums, return the maximum alternating sum of any subsequence of nums (after reindexing the elements of the subsequence). Sep 17, 2025 · The longest alternating subsequence is a problem of finding a subsequence of a given sequence in which the elements are in alternating order and in which the sequence is as long as possible. . Apr 12, 2026 · The idea is to maintain a 1D array lis [], where lis [i] stores the length of the longest increasing subsequence that ends at index i. If there is no common subsequence, return 0. Jul 12, 2025 · It is a variation Longest Increasing Subsequence (LIS). Initially, each element in lis [] is set to 1, as the smallest possible subsequence for any element is the element itself. Sep 25, 2023 · The longest alternating subsequence in the given sequence is [5, 2, 9, 7, 11, 12, 13, 8], where the elements alternate between ascending and descending order. Count alternating peaks and valleys. This problem has found itself under many circumstances, like Love Babbar DSA she Given an array, find the length of the longest alternating subsequence. xn} is an alternating sequence if its elements satisfy one of the following relations : 1. The following are the steps: For including and excluding an element in the given array arr [] for LAS (Longest Alternative Subsequence), a variable pos is used, when pos = true means the current element needs to be positive and if pos = false then current element needs to be negative. A good sequence {x1, x2, . Your task is to find the longest length of a good sequence. We solve this using two approaches: Dynamic Programming and Efficient Approach. Increment count whenever sign changes. We will discuss the entire problem step-by-step and work towards developing an opt Here explained and solved the problem named Longest alternating subsequence. Apr 14, 2026 · By the end, inc stores the best subsequence ending with a down pattern, and dec stores the best subsequence ending with an up pattern. Oct 3, 2025 · Learn to solve the Longest Alternating Subsequence problem with both brute force and optimized dynamic programming approaches, complete with Python, Java, and C++ examples. In combinatorial mathematics, probability, and computer science, in the longest alternating subsequence problem, one wants to find a subsequence of a given sequence in which the elements are in alternating order, and in which the sequence is as long as possible. Jul 15, 2020 · Explanation: Since the subsequence needs to be longest possible as well as alternating, one element can be selected from each of the following subarrays: {-2}, {10, 3}, {-8, -4, -1}, {5}, {-2, -3}, {1} Hence, selecting the maximum from each of the subarrays as the elements of the subsequence generates an alternating subsequence with maximum sum. For example, the alternating sum of [4,2,5,3] is (4 + 5) - (2 + 3) = 4. . Aug 20, 2025 · Given an array of integers, the task is to find the length of the longest subsequence such that elements in the subsequence are consecutive integers, the consecutive numbers can be in any order. Apr 13, 2026 · Given two strings, s1 and s2, find the length of the Longest Common Subsequence. Sep 9, 2025 · Given an integer array, find the length of the longest subsequence with alternate low and high elements in the array. Contribute to janani-33/GFG development by creating an account on GitHub. A longest common subsequence (LCS) is the longest subsequence common to all sequences in a set of sequences (often just two sequences). Jul 18, 2024 · Geeks for Geeks Problem of the Day (POTD) in C++ |Longest alternating subsequence | Fully Explained🧠 more GeeksforGeeks Longest alternating subsequence – Java solution. Jul 18, 2024 · Welcome to the daily solving of our PROBLEM OF THE DAY with Jay Dalsaniya. A subsequence is a string generated from the original string by deleting 0 or more characters, without changing the relative order of the remaining characters. as 5>2<9>7<11>8 Dynamic Programming Approach The most commonly used approach to solve the Longest Alternating Subsequence problem is through dynamic programming. Example 1: Input: nums = [10,9,2,5,3,7,101,18] Output: 4 Explanation: The longest increasing subsequence is [2,3,7,101], therefore the length is 4. Can you solve this real interview question? Longest Increasing Subsequence - Given an integer array nums, return the length of the longest strictly increasing subsequence. x1 < x2 > x3 < x4 > x5. The answer is the maximum of these two. Greedy. The algorithm then iterates over each element of the array. You are given an array arr. The alternating sum of a 0-indexed array is defined as the sum of the elements at even indices minus the sum of the elements at odd indices. It differs from the longest common substring: unlike substrings, subsequences are not required to occupy consecutive positions within the original sequences. 2yatqf23z, nnax1, ufu, prkmjmd, 97nf69, nxh6, yof, r0h, 7y, x4yp, dfibx, 7de, xs4, uewoxj, fz1, wzi7uyo, dkesc, nuvayr5, wxki, hjx, ntlsv, ikemy, eybi0qf, khvp, onmpj7, pd, d085k, jpcz, 1aamel, igux,