Trie insertion and query

main.rs

struct TrieNode {
    is_terminal: bool,
    children: [Option<Box<TrieNode>>; 256],
}

impl TrieNode {
    fn new() -> TrieNode {
        let mem : TrieNode = unsafe { std::mem::zeroed() };
        mem
    }

    fn find_word(&self, word: &str) -> bool {
        self.find_bytes(word.as_bytes())
    }

    fn append_word(&mut self, word: &str) {
        self.append_bytes(word.as_bytes());
    }

    fn find_bytes(&self, word: &[u8]) -> bool {
        let len = word.len();
        if len == 0 {
            return self.is_terminal;
        }
        let c = word[0];
        let index = c as usize;
        let child = &self.children[index];
        match *child {
            None => false,
            Some(ref p) => { (*p).find_bytes(&word[1 .. len]) }
        }
    }

    fn append_bytes(&mut self, word: &[u8]) {
        let len = word.len();
        if len == 0 {
            self.is_terminal = true;
        } else {
            let c = word[0];
            let index = c as usize;
            let mut child = &mut self.children[index];
            if child.is_none() {
                *child = Some(Box::new(TrieNode::new()));
            }
            match *child {
                None => { panic!("???"); }
                Some(ref mut p) => { (*p).append_bytes(&word[1 .. len]); }
            }
        }
    }
}

fn main() {
    let mut root = TrieNode::new();
    root.append_word("ad");
    println!("a  => {}", root.find_word("a"));
    println!("ad => {}", root.find_word("ad"));
    println!("an => {}", root.find_word("an"));
    println!("by => {}", root.find_word("by"));
    println!("");
    root.append_word("an");
    println!("a  => {}", root.find_word("a"));
    println!("ad => {}", root.find_word("ad"));
    println!("an => {}", root.find_word("an"));
    println!("by => {}", root.find_word("by"));
    println!("");
    root.append_word("a");
    println!("a  => {}", root.find_word("a"));
    println!("ad => {}", root.find_word("ad"));
    println!("an => {}", root.find_word("an"));
    println!("by => {}", root.find_word("by"));
}