APT: DNA Reverse

Class

public class DNAReverse { public String reverse(String dna) { // fill in code here } }

Problem Statement

When sequencing DNA we often don't know if the digital output from the sequencer represents a 3'-5' strand or 5'-3' strand. To help determine the correct orientation we'd like to obtain the reverse of a specific strand, e.g., from "gcat" the reverse strand would be "tacg" (no complementary base-pairs are calculated, the strand is simply reversed.)

For a given strand of DNA represented as a string, return the reverse of the strand, also as a string.

The DNA strand will contain only cytosine, guanine, thymine, and adenine, represented by the characters 'c', 'g', 't', and 'a', respectively.

Constraints

The String dna will contain at most 50 characters.
The characters of dna will be one of 'a', 'g', 't', 'c', all lower-case.

Examples

```
 "aaggttcc"

 Returns: "ccttggaa"
```
```
 "atgta"

 Returns: "atgta"
```
If the string is a palindrome, it's reverse is also a palindrome.
```
 "ccggttaat"

 Returns: "taattggcc"
```
```
 "t"

 Returns: "t"
```