refactor

rust/nucleotide-count/src/lib.rs

@@ -1,32 +1,28 @@
 use std::collections::HashMap;
 
 pub fn count(nucleotide: char, dna: &str) -> Result<usize, char> {
-    if !valid_nucleotide(nucleotide) {
+    if !is_valid_nucleotide(nucleotide) {
         return Err(nucleotide);
     }
     let counts = nucleotide_counts(dna)?;
     Ok(*counts.get(&nucleotide).unwrap())
 }
 
 pub fn nucleotide_counts(dna: &str) -> Result<HashMap<char, usize>, char> {
+    let mut counts = default_counts();
     for c in dna.chars() {
-        if !valid_nucleotide(c) {
+        if !is_valid_nucleotide(c) {
             return Err(c);
         }
-    }
-    let mut counts: HashMap<char, usize> = default_map();
-    for c in dna.chars() {
-        let default: usize = 0;
-        let v = counts.get(&c).unwrap_or(&default);
-        counts.insert(c, v + 1);
+        *counts.entry(c).or_insert(0) += 1;
     }
     Ok(counts)
 }
 
-fn default_map() -> HashMap<char, usize> {
+fn default_counts() -> HashMap<char, usize> {
     HashMap::from([('A', 0), ('C', 0), ('G', 0), ('T', 0)])
 }
 
-fn valid_nucleotide(c: char) -> bool {
+fn is_valid_nucleotide(c: char) -> bool {
     matches!(c, 'A' | 'C' | 'G' | 'T')
 }