1 class Solution { 2 public List<String> findWords(char[][] board, String[] words) { 3 List<String> res = new ArrayList<>(); 4 TrieNode root = buildTrie(words); 5 for (int i = 0; i < board.length; i++) { 6 for (int j = 0; j < board[0].length; j++) { 7 dfs (board, i, j, root, res); 8 } 9 } 10 return res; 11 } 12 13 public void dfs(char[][] board, int i, int j, TrieNode p, List<String> res) { 14 char c = board[i][j]; 15 if (c == '#' || p.next[c - 'a'] == null) return; 16 p = p.next[c - 'a']; 17 if (p.word != null) { // found one 18 res.add(p.word); 19 p.word = null; // de-duplicate 20 } 21 22 board[i][j] = '#'; 23 if (i > 0) dfs(board, i - 1, j ,p, res); 24 if (j > 0) dfs(board, i, j - 1, p, res); 25 if (i < board.length - 1) dfs(board, i + 1, j, p, res); 26 if (j < board[0].length - 1) dfs(board, i, j + 1, p, res); 27 board[i][j] = c; 28 } 29 30 public TrieNode buildTrie(String[] words) { 31 TrieNode root = new TrieNode(); 32 for (String w : words) { 33 TrieNode p = root; 34 for (char c : w.toCharArray()) { 35 int i = c - 'a'; 36 if (p.next[i] == null) p.next[i] = new TrieNode(); 37 p = p.next[i]; 38 } 39 p.word = w; 40 } 41 return root; 42 } 43 44 class TrieNode { 45 TrieNode[] next = new TrieNode[26]; 46 String word; 47 } 48 }
参考：https://leetcode.com/problems/word-search-ii/discuss/59780/Java-15ms-Easiest-Solution-(100.00)
