feat: word-search

Author: junbinding

trie.implement-trie-prefix-tree.py

@@ -17,10 +17,7 @@ def insert(self, word: str) -> None:
         """
         tree = self.lookup
         for a in word:
-            if a not in tree:
-                tree[a] = {}
-
-            tree = tree[a]
+            tree = tree.setdefault(a, {})
         tree['#'] = '#'
 
 
@@ -30,10 +27,7 @@ def search(self, word: str) -> bool:
         """
         tree = self.lookup
         for a in word:
-            if a not in tree:
-                return False
-
-            tree = tree[a]
+            tree = tree.setdefault(a, {})
 
         if '#' in tree:
             return True
@@ -47,11 +41,7 @@ def startsWith(self, prefix: str) -> bool:
         """
         tree = self.lookup
         for a in prefix:
-            if a not in tree:
-                return False
-
-            tree = tree[a]
-
+            tree = tree.setdefault(a, {})
         return True
 
 

trie.word-search.py

@@ -0,0 +1,52 @@
+from typing import List
+
+
+class Solution:
+    """
+    79. 单词搜索
+    https://leetcode-cn.com/problems/word-search/
+    给定一个二维网格和一个单词，找出该单词是否存在于网格中。
+    单词必须按照字母顺序，通过相邻的单元格内的字母构成，其中“相邻”单元格是那些水平相邻或垂直相邻的单元格。同一个单元格内的字母不允许被重复使用。
+    """
+
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        # 定义方向，上下右左
+        directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
+
+        def check(i: int, j: int, k: int) -> bool:
+            if board[i][j] != word[k]:
+                return False
+            if k == len(word) - 1:
+                return True
+
+            visited.add((i, j))
+            result = False
+            for di, dj in directions:
+                newi, newj = i + di, j + dj
+                if 0 <= newi < len(board) and 0 <= newj < len(board[0]):
+                    if (newi, newj) not in visited:
+                        if check(newi, newj, k + 1):
+                            result = True
+                            break
+
+            visited.remove((i, j))
+            return result
+
+        h, w = len(board), len(board[0])
+        visited = set()
+        for i in range(h):
+            for j in range(w):
+                if check(i, j, 0):
+                    return True
+
+        return False
+
+
+so = Solution()
+board = [
+  ['A','B','C','E'],
+  ['S','F','C','S'],
+  ['A','D','E','E']
+]
+
+print(so.exist(board, 'ABCCEDF'))