use std::collections::HashSet;
/*
Normalize a string:
- Convert letters to lowercase
- Replace any non-letter with a space
This ensures consistent word comparison.
*/
fn normalize(text: &str) -> String {
let mut result = String::with_capacity(text.len());
for ch in text.chars() {
if ch.is_ascii_alphabetic() {
result.push(ch.to_ascii_lowercase());
} else {
result.push(' ');
}
}
result
}
/*
Extract words from a string.
This function:
- Normalizes the input
- Splits on whitespace
- Filters out empty entries
- Returns a HashSet<String> for fast lookup and automatic duplicate removal
*/
fn extract_words(text: &str) -> HashSet<String> {
let normalized = normalize(text);
normalized
.split_whitespace()
.map(|w| w.to_string())
.collect::<HashSet<String>>()
}
/*
Find common words between two strings.
This function:
- Extracts words from both strings
- Uses set intersection for efficiency
- Returns a Vec<String> containing the common words
*/
fn find_common_words(a: &str, b: &str) -> Vec<String> {
let words_a = extract_words(a);
let words_b = extract_words(b);
words_a
.intersection(&words_b)
.cloned()
.collect::<Vec<String>>()
}
fn main() {
let s1 = "The quick brown fox jumps over the lazy dog.";
let s2 = "A lazy dog sleeps while the quick fox runs away.";
let mut common = find_common_words(s1, s2);
// Sort for stable output
common.sort();
println!("Common words:");
for w in common {
println!("{}", w);
}
}
/*
run:
Common words:
dog
fox
lazy
quick
the
*/
