Given an input string (s
) and a pattern (p
), implement regular expression matching with support for '.'
and '*'
.
'.' Matches any single character. '*' Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
Note:
s
could be empty and contains only lowercase lettersa-z
.p
could be empty and contains only lowercase lettersa-z
, and characters like.
or*
.
Example 1:
Input: s = "aa" p = "a" Output: false Explanation: "a" does not match the entire string "aa".
Example 2:
Input: s = "aa" p = "a*" Output: true Explanation: '*' means zero or more of the precedeng element, 'a'. Therefore, by repeating 'a' once, it becomes "aa".
Example 3:
Input: s = "ab" p = ".*" Output: true Explanation: ".*" means "zero or more (*) of any character (.)".
Example 4:
Input: s = "aab" p = "c*a*b" Output: true Explanation: c can be repeated 0 times, a can be repeated 1 time. Therefore it matches "aab".
Example 5:
Input: s = "mississippi" p = "mis*is*p*." Output: false
public boolean isMatch(String s, String p) { //return s.matches(p); Boolean[][] dp = new Boolean[s.length() + 1][p.length() + 1]; return isMatch(s, 0, p, 0, dp); } private boolean isMatch(String s, int i, String p, int j, Boolean[][] dp) { if (j == p.length()) { return i == s.length(); } if (dp[i][j] != null) { return dp[i][j]; } boolean ans; boolean matchFirstChar = i < s.length() && (s.charAt(i) == p.charAt(j) || p.charAt(j) == '.'); if (j + 1 < p.length() && p.charAt(j + 1) == '*') { boolean matchZero = isMatch(s, i, p, j + 2, dp); boolean matchOne = matchFirstChar && isMatch(s, i + 1, p, j, dp); ans = matchZero || matchOne; } else { ans = matchFirstChar && isMatch(s, i + 1, p, j + 1, dp); } dp[i][j] = ans; return ans; }