Word Search II

NeetCode/word-search-2/step1.py

@@ -0,0 +1,112 @@
+"""
+まあwordsをtrieにしてもよいかも
+TrieNodeのメソッドにaddとかがあったほうが良い
+"""
+
+class Node:
+    def __init__(self):
+        self.children = {}
+
+# TLE
+class Solution:
+    def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
+        num_rows = len(board)
+        num_cols = len(board[0])
+        visited = [[False] * num_cols for _ in range(num_rows)]
+        directions = [(0, 1), (0, -1), (1, 0), (-1, 0)]
+
+        def add(r, c, node):
+            visited[r][c] = True
+            if board[r][c] not in node.children: 
+                node.children[board[r][c]] = Node()
+
+            for dx, dy in directions:
+                next_r = r + dx
+                next_c = c + dy
+                if not (0 <= next_r < num_rows and 0 <= next_c < num_cols and not visited[next_r][next_c]):
+                    continue
+                add(next_r, next_c, node.children[board[r][c]])
+
+            visited[r][c] = False
+
+        def search(word):
+            curr = root
+            for c in word:
+                if c not in curr.children:
+                    return False
+                curr = curr.children[c]
+            return True
+
+        root = Node()
+        for r in range(num_rows):
+            for c in range(num_cols):
+                add(r, c, root)
+
+        detected_words = []
+        for word in words:
+            if search(word):
+                detected_words.append(word)
+        return detected_words
+
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.is_word = False
+        self.refs = 0
+
+    def add_word(self, word):
+        curr = self
+        curr.refs += 1
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+            curr.refs += 1
+        curr.is_word = True
+
+    def remove_word(self, word):
+        curr = self
+        curr.refs -= 1
+        for c in word:
+            curr = curr.children[c]
+            curr.refs -= 1
+        curr.is_word = False
+
+class Solution:
+    def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
+        root = TrieNode()
+        for word in words:
+            root.add_word(word)
+
+        num_rows = len(board)
+        num_cols = len(board[0])
+        visited = set()
+        found_words = []
+
+        def dfs(r, c, node, curr_word):
+            if (
+                r not in range(num_rows) or
+                c not in range(num_cols) or
+                (r, c) in visited or
+                board[r][c] not in node.children or
+                node.children[board[r][c]].refs == 0
+            ): return
+
+            visited.add((r, c))
+            curr_word += board[r][c]
+            node = node.children[board[r][c]]
+            if node.is_word:
+                found_words.append(curr_word)
+                root.remove_word(curr_word)
+
+            dfs(r + 1, c, node, curr_word)
+            dfs(r - 1, c, node, curr_word)
+            dfs(r, c + 1, node, curr_word)
+            dfs(r, c - 1, node, curr_word)
+            visited.remove((r, c))
+
+        for r in range(num_rows):
+            for c in range(num_cols):
+                dfs(r, c, root, "")
+
+        return found_words

NeetCode/word-search-2/step3.py

@@ -0,0 +1,62 @@
+class TrieNode:
+    def __init__(self):
+        self.children = {}
+        self.is_word = False
+        self.refs = 0
+
+    def add_word(self, word):
+        curr = self
+        curr.refs += 1
+        for c in word:
+            if c not in curr.children:
+                curr.children[c] = TrieNode()
+            curr = curr.children[c]
+            curr.refs += 1
+        curr.is_word = True
+
+    def remove_word(self, word):
+        curr = self
+        curr.refs -= 1
+        for c in word:
+            curr = curr.children[c]
+            curr.refs -= 1
+        curr.is_word = False
+
+class Solution:
+    def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
+        root = TrieNode()
+        for word in words:
+            root.add_word(word)
+
+        found_words = []
+        num_rows = len(board)
+        num_cols = len(board[0])
+        visited = set()
+
+        def dfs(r, c, node, word):
+            if (
+                r not in range(num_rows) or
+                c not in range(num_cols) or
+                (r, c) in visited or
+                board[r][c] not in node.children or
+                node.children[board[r][c]].refs == 0
+            ): return
+
+            visited.add((r, c))
+            word += board[r][c]
+            node = node.children[board[r][c]]
+            if node.is_word:
+                found_words.append(word)
+                root.remove_word(word)
+
+            dfs(r + 1, c, node, word)
+            dfs(r - 1, c, node, word)
+            dfs(r, c + 1, node, word)
+            dfs(r, c - 1, node, word)
+            visited.remove((r, c))
+
+        for r in range(num_rows):
+            for c in range(num_cols):
+                dfs(r, c, root, "")
+
+        return found_words