Problem: DNA-2, CG counting

Problem Statement

Given a strand of DNA determine the percentage of cytosine and guanine nucleotides present in the genome. The strand is represented by a string containing only the lowercase characters 'c', 'g', 't', and 'a'. Your method should return the percentage (between 0.0 and 1.0) of 'c' (cytosine) and 'g' (guanine) in the genome. For example, if half of the nucleotides are 'c' or 'g' your method should return 0.5.

Definition

Class: DNAcgcount
Method: ratio
Parameters: String
Returns: double
Method signature:
```
  double ratio(String dna)
```
(be sure your method is public)

Class
public class DNAcgcount { public double ratio(String dna) { // fill in code here } };
Constraints
- The String dna contains only the characters 'a', 'g', 't', 'c' (lowercase).
- The String dna is between 0 and 1000 characters long (inclusive).
Examples
1. ```
"agatc"
```
  Returns:0.40
  There is one guanine and one cytosine for two out of five or 40% (which is 0.4)
2. ```
"catatggatatc"
```
  Returns: 0.3333333 (don't worry about round off problems, if your answer is close---within 10^-6---it will be correct).
Owen L. Astrachan
Last modified: Wed Sep 7 12:28:05 EDT 2005

Problem: DNA-2, CG counting

Problem Statement

Definition

Class

Constraints

Examples