String Types

String Types in Rust

Rust has two main string types:

String — Owned, heap-allocated

String is a growable, heap-allocated UTF-8 string. You own it, and it is dropped when it goes out of scope:

let mut s = String::from("hello");
s.push_str(", world"); // mutate in place
s.push('!');
println!("{}", s); // hello, world!

&str — Borrowed string slice

&str is a reference to a sequence of UTF-8 bytes. String literals like "hello" are &str:

let s: &str = "hello"; // string literal — stored in binary

Converting Between Them

let owned: String = "hello".to_string();
let owned2: String = String::from("hello");
let borrowed: &str = &owned; // auto-deref

Useful String Methods

let s = "Hello, World!";
s.len()               // 13 (bytes, not chars)
s.contains("World")   // true
s.to_lowercase()      // "hello, world!"
s.trim()              // strips whitespace
s.split(", ")         // iterator of parts
s.chars()             // iterator of chars

format!

Build strings dynamically with format! — just like println! but returns a String:

let name = "Alice";
let greeting = format!("Hello, {}!", name);

Your Task

1. is_palindrome(s: &str) -> bool — returns true if the string reads the same forward and backward.
2. count_vowels(s: &str) -> usize — counts vowels (a, e, i, o, u, case-insensitive).
3. title_case(s: &str) -> String — capitalizes the first letter of each word.