anagram

rust/anagram/src/lib.rs

@@ -1,8 +1,36 @@
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 
-pub fn anagrams_for<'a>(
-        word: &str, 
-        possible_anagrams: &[&str]
-    ) -> HashSet<&'a str> {
-    todo!("For the '{word}' word find anagrams among the following words: {possible_anagrams:?}");
+pub trait CharCounter {
+    fn get_chars_frequency(&self) -> HashMap<char, usize>;
+}
+
+pub trait AnagramsFinder<'a> {
+    fn find_anagrams(&self, pattern_raw: &str) -> HashSet<&'a str>;
+}
+
+impl CharCounter for str {
+    fn get_chars_frequency(&self) -> HashMap<char, usize> {
+        self.chars().fold(HashMap::new(), |mut acc, c| {
+            *acc.entry(c).or_insert(0) += 1;
+            acc
+        })
+    }
+}
+
+impl<'a> AnagramsFinder<'a> for [&'a str] {
+    fn find_anagrams(&self, pattern_raw: &str) -> HashSet<&'a str> {
+        let pattern = pattern_raw.to_lowercase();
+        let pattern_map: HashMap<char, usize> = pattern.get_chars_frequency();
+        self.iter()
+            .copied()
+            .filter(|word_raw| {
+                let word = word_raw.to_lowercase();
+                word != pattern && word.get_chars_frequency() == pattern_map
+            })
+            .collect()
+    }
+}
+
+pub fn anagrams_for<'a>(word: &str, possible_anagrams: &[&'a str]) -> HashSet<&'a str> {
+    possible_anagrams.find_anagrams(word)
 }