Regular Expression Matching

Desicription

Implement regular expression matching with support for '.' and '*'.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
'.' Matches any single character.
'*' Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
The function prototype should be:
bool isMatch(const char *s, const char *p)
Some examples:
isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true

Solution

1
2
3
4
5
6
7
8
9
10
11
class Solution {
public:
bool isMatch(string s, string p) {
if(p.empty())
return s.empty();
if(p[1] == '*')
return isMatch(s, p.substr(2)) || (!s.empty() && (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p));
else
return !s.empty() && (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p.substr(1));
}
};