Feature #7: Detecting a Protein

Description

Proteins are characterized by long palindrome sequences of nucleotides, where a character represents each nucleotide. We have received a sample that may be a protein. However, the nucleotides in this sample may have been rearranged due to a mutation.

Given a sequence of nucleotides, our task is to check if any permutationOrdering of a set of items; in this case, the sequences of nucleotides. of the given sequence is a protein, that is, a palindromeA word spelled the same way forwards as backward.. We should return true if it is a protein, and return false if it is not a protein.

The following examples may help to clarify this problem:

Solution

If some permutation of a sequence with an even length is a palindrome, every nucleotide in the sequence must appear an even number of times. Similarly, if a permutation of a sequence with an _odd length _is a palindrome, every nucleotide, except one, must appear an even number of times. So, in the case of a sequence being a palindrome and when there is a sequence of an odd length, the number of nucleotides with an odd number of occurrences cannot exceed 1. Similarly, in the case of a sequence with an even length, the number of nucleotides with an odd number of occurrences is 0.

Suppose we are given a sequence, s, and we expect all the nucleotides in s to appear an even number of times, except for perhaps one of them. So we can check if a nucleotide appears an odd number of times in the sequence. If more than one nucleotides appear an odd number of times, then s cannot be a palindrome. To do so, we can use a hashmap that stores the ...