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How to find longest alternating subsequence?
Input: arr[] = {1, 5, 4} Output: 3 The whole arrays is of the form x1 < x2 > x3 Input: arr[] = {1, 4, 5} Output: 2 All subsequences of length 2 are either of the form x1 < x2; or x1 > x2 Input: arr[] = {10, 22, 9, 33, 49, 50, 31, 60} Output: 6 The subsequences {10, 22, 9, 33, 31, 60} or {10, 22, 9, 49, 31, 60} or {10.
How do you find alternating subsequence?
Taking a variable and initializing it with the first value of the array and then comparing it with other values will find the min. Check if the min is equal to arr[0]. If it is true then arr[0] is to be returned, because there is no decreasing step available to find an alternating subsequence.
What is zig zag sequence?
A sequence will be called a zig zag sequence if the first elements in the sequence are in increasing order and the last elements are in decreasing order, where . You need to find the lexicographically smallest zig zag sequence of the given array. Example.
What is zig zag coding in multimedia?
In coding theory, a zigzag code is a type of linear error-correcting code introduced by Ping, Huang & Phamdo (2001). The code rate is high: J/(J + 1) where J is the number of bits per segment.
What bitonic subsequence is longest?
The longest bitonic subsequence problem is to find a subsequence of a given sequence in which the subsequence’s elements are first sorted in increasing order, then in decreasing order, and the subsequence is as long as possible.
Which is the longest alternating sequence in an array?
The task is to find the length of the longest alternating (means negative-positive-negative or positive-negative-positive) subsequence present in the array . The longest sequence is {-4, 3, -5, 9, -1}, which is of length 5. There can be many more subsequences of this length.
What is the problem of the longest alternating subsequence?
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. In order words, we need to find the length of the longest subsequence with alternate low and high elements.
When to increase Inc and DEC in subsequence?
The tricky part of this approach is to update these two values. “inc” should be increased, if and only if the last element in the alternative sequence was smaller than it’s previous element. “dec” should be increased, if and only if the last element in the alternative sequence was greater than it’s previous element.