update

hard/212.word-search-ii.java

@@ -14,60 +14,39 @@ class Solution {
         if ((n = board.length) == 0 || (m = board[0].length) == 0 || words.length == 0) return res;
         this.board = board;
         root = new TrieNode();
-        root.cnt = -1;
         for (String word : words) root.insert(word);
-        for (int y = 0; y < n; y++) {
-            for (int x = 0; x < m; x++) {
-                StringBuilder sb = new StringBuilder();
-                backtrack(y, x, root, sb, res);
-            }
-        }
+        for (int y = 0; y < n; y++)
+            for (int x = 0; x < m; x++)
+                backtracking(y, x, root, res);
         return res;
     }
 
-    private void backtrack(int y, int x, TrieNode curr, StringBuilder sb, LinkedList<String> res) {
-        if (curr == null || curr.cnt == 0) return;
-        if (curr.isKey) {
-            res.add(sb.toString());
-            root.remove(sb.toString());
+    private void backtracking(int y, int x, TrieNode curr, LinkedList<String> res) {
+        if (curr == null) return;
+        if (curr.word != null) {
+            res.add(curr.word);
+            curr.word = null;
         }
         char c;
         if (y < 0 || n <= y || x < 0 || m <= x || (c = board[y][x]) == '#') return;
-        sb.append(c);
         board[y][x] = '#';
-        curr = curr.next[(int) c - 'a'];
-        for (int i = 0; i < 4; i++) {
-            int ny = y + dy[i], nx = x + dx[i];
-            backtrack(ny, nx, curr, sb, res);
-        }
-        sb.deleteCharAt(sb.length() - 1);
+        curr = curr.next[c - 'a'];
+        for (int i = 0; i < 4; i++) backtracking(y + dy[i], x + dx[i], curr, res);
         board[y][x] = c;
     }
 
     class TrieNode {
-        int cnt;
-        boolean isKey;
+        String word;
         TrieNode[] next = new TrieNode[26];
 
         void insert(String str) {
             TrieNode curr = this;
             for (char c : str.toCharArray()) {
-                int i = (int) c - 'a';
+                int i = c - 'a';
                 if (curr.next[i] == null) curr.next[i] = new TrieNode();
                 curr = curr.next[i];
-                curr.cnt++;
-            }
-            curr.isKey = true;
-        }
-
-        void remove(String str) {
-            TrieNode curr = this;
-            for (char c : str.toCharArray()) {
-                int i = (int) c - 'a';
-                curr = curr.next[i];
-                curr.cnt--;
             }
-            curr.isKey = false;
+            curr.word = str;
         }
     }
 }