[LeetCode]208. Implement Trie (Prefix Tree)

Problem Description

[https://leetcode.com/problems/implement-trie-prefix-tree/]
Implement a trie with insert, search, and startsWith methods.

思路

沒啥好說的，看代碼就好惹。。

Code

package q208;

import java.util.LinkedList;

class TrieNode {
    // Initialize your data structure here.
    LinkedList<TrieNode> sons = new LinkedList<TrieNode>();
    char c;
    int sum;

    public TrieNode() {
    }

    public TrieNode(char c) {
        this.c = c;
        this.sum = 1;
    }

    public TrieNode(TrieNode father, char c) {
        this.c = c;
        this.sum = 1;
        father.sons.add(this);
    }
}

public class Trie {
    private TrieNode root;

    public Trie() {
        root = new TrieNode();
    }

    // Inserts a word into the trie.
    public void insert(String word) {
        TrieNode tmp = root;
        boolean find;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            LinkedList<TrieNode> sons = tmp.sons;
            find = false;
            for (int j = 0; j < sons.size(); j++) {
                if (sons.get(j).c == c) {
                    tmp = sons.get(j);
                    tmp.sum++;
                    find = true;
                    break;
                }
            }
            if (!find) {
                TrieNode tmp2 = new TrieNode(tmp, c);
                tmp = tmp2;
                // System.out.println(tmp.sons.get(tmp.sons.size()-1).c);
            }
        }
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
        TrieNode tmp = root;
        boolean find;
        for (int i = 0; i < word.length(); i++) {
            char c = word.charAt(i);
            LinkedList<TrieNode> sons = tmp.sons;
            find = false;
            for (int j = 0; j < sons.size(); j++) {
                if (sons.get(j).c == c) {
                    tmp = sons.get(j);
                    find = true;
                    break;
                }
            }
            if (!find) {
                return false;
            }
        }
        if (tmp.sons.size() > 0) {
            int sum = 0;
            LinkedList<TrieNode> sons = tmp.sons;
            for (int j = 0; j < sons.size(); j++) {
                sum += sons.get(j).sum;
            }
            if (sum == tmp.sum)
                return false;
        }
        return true;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode tmp = root;
        boolean find;
        for (int i = 0; i < prefix.length(); i++) {
            char c = prefix.charAt(i);
            LinkedList<TrieNode> sons = tmp.sons;
            find = false;
            for (int j = 0; j < sons.size(); j++) {
                if (sons.get(j).c == c) {
                    tmp = sons.get(j);
                    find = true;
                    break;
                }
            }
            if (!find) {
                return false;
            }
        }
        return true;
    }

//  public static void main(String[] args) {
//      Trie t = new Trie();
//      t.insert("abc");
//      System.out.println(t.search("abc"));
//      System.out.println(t.search("ab"));
//      t.insert("ab");
//      System.out.println(t.search("ab"));
//      t.insert("ab");
//      System.out.println(t.search("ab"));
//
//  }

}