# -*- mode: snippet -*-
# name: z algorithm
# contributor: Nakamura Kenko
# key: zalgorithm
# --

pub mod z_algorithm {

    pub fn calc_z_array<T: PartialEq>(s: &[T]) -> Vec<usize> {
        let n = s.len();
        let mut z_array = vec![0; n];

        // [l, r) is a window which matches with prefix of s
        let mut l = 0;
        let mut r = 1;
        for i in 1..n {
            if i >= r {
                l = i;
                r = i + 1;
                while r <= n && s[r - 1 - l] == s[r - 1] {
                    r += 1;
                }
                z_array[i] = r - l - 1;
                r -= 1;
            } else if z_array[i - l] < r - i {
                z_array[i] = z_array[i - l];
            } else {
                l = i;
                while r <= n && s[r - 1 - l] == s[r - 1] {
                    r += 1;
                }
                z_array[i] = r - l - 1;
                r -= 1;
            }
        }
        z_array[0] = n;
        z_array
    }
}

