题目：

题解：

class Solution {Trie trie = new Trie();public List<String> findAllConcatenatedWordsInADict(String[] words) {List<String> ans = new ArrayList<String>();Arrays.sort(words, (a, b) -> a.length() - b.length());for (int i = 0; i < words.length; i++) {String word = words[i];if (word.length() == 0) {continue;}boolean[] visited = new boolean[word.length()];if (dfs(word, 0, visited)) {ans.add(word);} else {insert(word);}}return ans;}public boolean dfs(String word, int start, boolean[] visited) {if (word.length() == start) {return true;}if (visited[start]) {return false;}visited[start] = true;Trie node = trie;for (int i = start; i < word.length(); i++) {char ch = word.charAt(i);int index = ch - 'a';node = node.children[index];if (node == null) {return false;}if (node.isEnd) {if (dfs(word, i + 1, visited)) {return true;}}}return false;}public void insert(String word) {Trie node = trie;for (int i = 0; i < word.length(); i++) {char ch = word.charAt(i);int index = ch - 'a';if (node.children[index] == null) {node.children[index] = new Trie();}node = node.children[index];}node.isEnd = true;}
}class Trie {Trie[] children;boolean isEnd;public Trie() {children = new Trie[26];isEnd = false;}
}