[Fundamental] Implement Trie and Suffix Tree

Trie Node

public class TrieNode {
    boolean isLeaf;
    TrieNode[] child;

    public TrieNode(boolean isLeaf) {
        this.isLeaf = isLeaf;
        this.child = new TrieNode[26];
    }

    public void insert(String str) {
        if (str == null || str.length() == 0) {
            this.isLeaf = true;
            return;
        }
        char cur = str.charAt(0);
        if (child[cur - 'a'] == null) {
            child[cur - 'a'] = new TrieNode(str.length() == 1);
        }
        child[cur - 'a'].insert(str.substring(1));
    }

    public boolean trieSearch(String str) {
        // have to consider leaf node
        if (str == null || str.length() == 0) {
            return isLeaf;
        }
        char cur = str.charAt(0);
        if (child[cur - 'a'] == null) {
            return false;
        }
        return child[cur - 'a'].trieSearch(str.substring(1));
    }

    public boolean suffixTreeSearch(String str) {
        // suffixTreeSearch don't consider leaf node
        // cuz we search for prefix of suffixes
        if (str == null || str.length() == 0) {
            return true;
        }
        char cur = str.charAt(0);
        if (child[cur - 'a'] == null) {
            return false;
        }
        return child[cur - 'a'].suffixTreeSearch(str.substring(1));
    }
}

Trie

public class Trie {
    TrieNode root;

    public Trie(String[] input) {
        root = new TrieNode(false);

        for (String str : input) {
            root.insert(str);
        }
    }

    public boolean search(String query) {
        return root.trieSearch(query);
    }
}

Suffix Tree

Suffix tree might also consider the List of indexes thing, which I do not take into consideration in my code.

public class SuffixTree {
    TrieNode root;

    public SuffixTree(String input) {
        root = new TrieNode(false);

        for (int i = 0; i < input.length(); i++) {
            root.insert(input.substring(i));
        }
    }

    public boolean search(String query) {
        return root.suffixTreeSearch(query);
    }
}