Index out of bounds while checking if a string is rotated - indexing

Question

// This function checks if two string are rotation of itself
//
// #Arguments
//
// 'str1' - a str type reference to store one string to check
// 'str2' - a str type reference to store other string to check
//
// #Return
//
// Return a bool value denoting if the string are rotation of each other
pub fn is_rotation(str1: &str, str2: &str) -> bool {
let len1 = str1.len();
let len2 = str2.len();
let string1: Vec<char> = str1.chars().collect();
let string2: Vec<char> = str2.chars().collect();
if len1 != len2 {
return false;
}
let mut longest_prefix_suffix = vec![0, len1];
let mut prev_len = 0;
let mut i = 1;
while i < len1 {
if string1[i] == string2[prev_len] {
prev_len += 1;
longest_prefix_suffix[i] = prev_len;
i += 1;
} else if prev_len == 0 {
longest_prefix_suffix[i] = 0;
i += 1;
} else {
prev_len = longest_prefix_suffix[prev_len - 1];
}
}
i = 0;
let mut k = longest_prefix_suffix[len1 - 1];
while k < len2 {
if string2[k] != string1[i] {
return false;
}
i += 1;
k += 1;
}
true
}
When I run the code, I receive the following error:
thread 'main' panicked at 'index out of bounds: the len is 2 but the index is 2', src/rotation.rs:29:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
How would I solve this?

Answer 1

It looks like there is a typo for longest_prefix_suffix. I assume you intended to write the following:
let mut longest_prefix_suffix = vec![0; len1];
Note the ; between 0 and len1.
The use of a , created a Vec with two elements.
Alternatively, an easier way might be the following:
fn is_rotation(s1: &str, s2: &str) -> bool {
if s1.len() != s2.len() {
return false;
}
s1.repeat(2).contains(&s2)
}
assert!(is_rotation("hello", "ohell") // true
assert!(is_rotation("hello", "olleh") // false