Add 212_Word_Search_II.java

Author: Sean Prashad

Tree Depth First Search/212_Word_Search_II.java

@@ -0,0 +1,59 @@
+class TrieNode {
+ TrieNode[] children = new TrieNode[26];
+ String Word;
+}
+
+class Solution {
+ public List<String> findWords(char[][] board, String[] words) {
+ Set<String> result = new HashSet<>();
+ TrieNode root = buildTrie(words);
+ 
+ for (int i = 0; i < board.length; i++) {
+ for (int j = 0; j < board[i].length; j++) {
+ dfs(board, i, j, root, result);
+ }
+ }
+ 
+ return new ArrayList<>(result);
+ }
+ 
+ private void dfs(char[][] board, int x, int y, TrieNode root, Set<String> result) {
+ if (x < 0 || y < 0 || x >= board.length || y >= board[x].length || board[x][y] == '*' || root.children[board[x][y] - 'a'] == null) { return; }
+ 
+ char currChar = board[x][y];
+ root = root.children[currChar - 'a'];
+ 
+ if (root.Word != null) {
+ result.add(root.Word);
+ }
+ 
+ board[x][y] = '*';
+ 
+ dfs(board, x - 1, y, root, result);
+ dfs(board, x + 1, y, root, result);
+ dfs(board, x, y - 1, root, result);
+ dfs(board, x, y + 1, root, result);
+ 
+ board[x][y] = currChar;
+ }
+ 
+ private TrieNode buildTrie(String[] words) {
+ if (words == null) { return null; }
+ 
+ TrieNode root = new TrieNode();
+ for (String word : words) {
+ TrieNode curr = root;
+ for (char c : word.toCharArray()) {
+ int idx = c - 'a';
+ if (curr.children[idx] == null) {
+ curr.children[idx] = new TrieNode();
+ }
+ curr = curr.children[idx];
+ }
+ 
+ curr.Word = word;
+ }
+ 
+ return root;
+ }
+}