题目：原题链接（困难）
标签：回溯算法、字典树、深度优先搜索
解法 | 时间复杂度 | 空间复杂度 | 执行用时 |
Ans 1 (Python) | O ( M × N × 2 6 L ) | O ( M × N ) | 9848ms (5.06%) |
Ans 2 (Python) | |||
Ans 3 (Python) |
解法一：
class Solution:
def findWords(self, board: List[List[str]], words: List[str]) -> List[str]:
# 构造字典树
root = {}
for word in words:
node = root
for ch in word:
if ch not in node:
node[ch] = {}
node = node[ch]
node["#"] = word
m, n = len(board), len(board[0])
def is_valid(x, y):
return 0 <= x < m and 0 <= y < n
def neighbors(x, y):
return [(xx, yy) for xx, yy in [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)] if is_valid(xx, yy)]
# 深度优先搜索
def dfs(now, i1, j1, visited):
if board[i1][j1] not in now:
return
now = now[board[i1][j1]]
if "#" in now:
ans.add(now["#"])
for i2, j2 in neighbors(i1, j1):
if (i2, j2) not in visited:
visited.add((i2, j2))
dfs(now, i2, j2, visited)
visited.remove((i2, j2))
ans = set()
# 遍历二维网格
for i in range(m):
for j in range(n):
dfs(root, i, j, {(i, j)})
return list(ans)
