Feature #2: Detect Virus

Description

While studying different DNA samples, we observed that a certain virus consists of really long sequences of k distinct nucleotides. The virus infects a species by embedding itself into the species’s DNA. We are working on devising a test to detect the virus. The idea is to analyze the longest string that consists of, at most, k nucleotides from a species’s DNA.

We’ll be provided with a string representing a chromosome from the infected DNA and a k value supplied from a hidden function. Our task will include calculating the longest subsequence from the chromosome string that has k unique nucleotides.

Here is an illustration to better understand this process:

Solution

Since we want to return a substring from a specific window over the original string, we can use a sliding window approach to accomplish this efficiently. We’ll use two pointers, left and right, to denote ...