Create Word Search II.java

Author: sudoshivesh

hard/Word Search II.java

@@ -0,0 +1,56 @@
+//212. Word Search II
+class TrieNode {
+  public TrieNode[] children = new TrieNode[26];
+  public String word;
+}
+
+class Solution {
+  public List<String> findWords(char[][] board, String[] words) {
+    for (final String word : words)
+      insert(word);
+
+    List<String> ans = new ArrayList<>();
+
+    for (int i = 0; i < board.length; ++i)
+      for (int j = 0; j < board[0].length; ++j)
+        dfs(board, i, j, root, ans);
+
+    return ans;
+  }
+
+  private TrieNode root = new TrieNode();
+
+  private void insert(final String word) {
+    TrieNode node = root;
+    for (final char c : word.toCharArray()) {
+      final int i = c - 'a';
+      if (node.children[i] == null)
+        node.children[i] = new TrieNode();
+      node = node.children[i];
+    }
+    node.word = word;
+  }
+
+  private void dfs(char[][] board, int i, int j, TrieNode node, List<String> ans) {
+    if (i < 0 || i == board.length || j < 0 || j == board[0].length)
+      return;
+    if (board[i][j] == '*')
+      return;
+
+    final char c = board[i][j];
+    TrieNode child = node.children[c - 'a'];
+    if (child == null)
+      return;
+    if (child.word != null) {
+      ans.add(child.word);
+      child.word = null;
+    }
+
+    board[i][j] = '*';
+    dfs(board, i + 1, j, child, ans);
+    dfs(board, i - 1, j, child, ans);
+    dfs(board, i, j + 1, child, ans);
+    dfs(board, i, j - 1, child, ans);
+    board[i][j] = c;
+  }
+}