1. 题目

2. 读题（需要重点注意的东西）

3. 解法

详细的构建思路，请看下文 5. 所用到的数据结构与算法思想

class Trie {
          
   

	private class TrieNode {
          
   
		private boolean isEnd;
		private TrieNode[] next;

		public TrieNode() {
          
   
			isEnd = false;
			next = new TrieNode[26];
		}

	}

	private TrieNode root;

	/** Initialize your data structure here. */
	public Trie() {
          
   
		root = new TrieNode();
	}

	/** Inserts a word into the trie. */
	public void insert(String word) {
          
   
		TrieNode cur = root;
		for (int i = 0, len = word.length(), ch; i < len; i++) {
          
   
			ch = word.charAt(i) - a;
			if (cur.next[ch] == null)
				cur.next[ch] = new TrieNode();
			cur = cur.next[ch];
		}
		cur.isEnd = true;
	}

	/** Returns if the word is in the trie. */
	public boolean search(String word) {
          
   
		TrieNode cur = root;
		for (int i = 0, len = word.length(), ch; i < len; i++) {
          
   
			ch = word.charAt(i) - a;
			if (cur.next[ch] == null)
				return false;
			cur = cur.next[ch];
		}
		return cur.isEnd;
	}

	/**
	 * Returns if there is any word in the trie that starts with the given prefix.
	 */
	public boolean startsWith(String prefix) {
          
   
		TrieNode cur = root;
		for (int i = 0, len = prefix.length(), ch; i < len; i++) {
          
   
			ch = prefix.charAt(i) - a;
			if (cur.next[ch] == null)
				return false;
			cur = cur.next[ch];
		}
		return true;
	}
}
/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */

4. 可能有帮助的前置习题

5. 所用到的数据结构与算法思想

6. 总结

这是前缀树相关问题的基础，一般题目是不会给出前缀树的相关定义代码的，如果在解题中要利用前缀树，就必须自己在解题时定义。 如果无法实现，请看，并将代码熟记直至能够完整默写。