class IsMatch:
"""
10. 正则表达式匹配
https://leetcode.cn/problems/regular-expression-matching/description/
"""
def solution(self, s: str, p: str) -> bool:
m, n = len(s), len(p)
memo = [[-1] * n for _ in range(m)]
return self.dp(s, 0, p, 0, memo)
def dp(self, s: str, i: int, p: str, j: int, memo: list) -> bool:
m, n = len(s), len(p)
# base case 1
# 模式串 p 匹配完了，那要看文本串 s 是否匹配完
if j == n:
return i == m
# base case 2
# 文本串 s 匹配完了，那模式串 p 一定是 字符 和 * 成对出现的
if i == m:
# 检查是否成对
if (n - j) % 2 == 1:
return False
# 检查是否 x*y*z* 这种形式
for k in range(j + 1, n, 2):
if p[k] != '*':
return False
return True
# 备忘录
if memo[i][j] != -1:
return memo[i][j]
res = False
if s[i] == p[j] or p[j] == '.':
if j < n - 1 and p[j + 1] == '*':
# 通配符匹配0次
res = self.dp(s, i, p, j + 2, memo) or \
self.dp(s, i + 1, p, j, memo) # 通配符匹配多次
else:
# 常规匹配1次
res = self.dp(s, i + 1, p, j + 1, memo)
else:
if j < n - 1 and p[j + 1] == '*':
# 通配符匹配0次
res = self.dp(s, i, p, j + 2, memo)
else:
# 无法继续匹配
res = False
memo[i][j] = res
return res