Given an m x n board of characters and a list of strings words, return all words on the board.
Each word must be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.
class TrieNode:
def __init__(self):
self.is_leaf = False
self.children = {}
self.word = None
class TrieTree:
def __init__(self):
self.root = TrieNode()
self.word = False
def insert(self, s):
cur = self.root
for c in s:
if c not in cur.children:
cur.children[c] = TrieNode()
cur = cur.children[c]
cur.word = s
class Solution:
def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
tree = TrieTree()
for word in words:
tree.insert(word)
dirs = [(0, 1), (0, -1), (1, 0), (-1, 0)]
m, n = len(board), len(board[0])
ans = []
def backtrack(i, j):
nonlocal root
letter = board[i][j]
if letter not in root.children:
return
oldroot = root
root = root.children[letter]
board[i][j] = '#'
if root.word:
ans.append(root.word)
root.word = None
for dx, dy in dirs:
if 0 <= i + dx < m and 0 <= j + dy < n and board[i + dx][j + dy] != '#':
backtrack(i + dx, j + dy)
board[i][j] = letter
root = oldroot
for i in range(m):
for j in range(n):
root = tree.root
backtrack(i, j)
return ans