/*
-------------------------------------------------------------------------
What is a trigram?
-------------------------------------------------------------------------
A trigram is a sequence of exactly three consecutive characters taken
from a word. To generate all trigrams, we slide a window of length 3
across the string. Each step produces a new 3‑character slice.
Example:
Word: "magic"
Trigrams: ["mag", "agi", "gic"]
Trigrams are useful in text processing, search algorithms,
and language modeling because they capture small structural patterns
inside words.
*/
use std::io::{self, Write};
/*
Function: make_trigrams
-----------------------
Returns a vector containing all trigrams of the given word.
Steps:
- If the word is shorter than 3 characters, return an empty vector.
- Otherwise, slide a window of size 3 across the word.
- Use slicing to extract each 3‑character sequence.
The algorithm runs in O(n) time and uses O(n) space.
Note:
Rust strings are UTF‑8, so slicing must be done on byte indices.
This function assumes ASCII input for simplicity.
*/
fn make_trigrams(word: &str) -> Vec<String> {
if word.len() < 3 {
return Vec::new();
}
let count = word.len() - 2;
let mut result: Vec<String> = Vec::with_capacity(count);
for i in 0..count {
result.push(word[i..i + 3].to_string());
}
result
}
/*
Main program:
- Read a word from the user.
- Generate trigrams.
- Print each trigram.
*/
fn main() {
print!("Enter a word: ");
io::stdout().flush().unwrap();
let mut input = String::new();
io::stdin().read_line(&mut input).unwrap();
let word = input.trim();
let trigrams = make_trigrams(word);
println!("\nTrigrams:");
for t in trigrams {
println!("{}", t);
}
}
/*
run:
Enter a word: computer
Trigrams:
com
omp
mpu
put
ute
ter
*/
