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).
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
1 public class Solution { 2 public bool IsMatch(string s, string p) 3 { 4 if (s == null || p == null) 5 { 6 return s == null && p == null; 7 } 8 9 return IsMatchInternal(s, p, 0, 0); 10 } 11 12 private bool IsMatchInternal(string source, string pattern, int sStart, int pStart) 13 { 14 if (sStart >= source.Length || pStart >= pattern.Length) 15 { 16 if (sStart >= source.Length && pStart >= pattern.Length) 17 { 18 return true; 19 } 20 21 if (pStart >= pattern.Length) 22 { 23 return false; 24 } 25 } 26 27 if (pStart < pattern.Length - 1) 28 { 29 if (pattern[pStart + 1] == ‘*‘) 30 { 31 if (IsMatchInternal(source, pattern, sStart, pStart + 2)) return true; 32 33 if (pattern[pStart] == ‘.‘) 34 { 35 for (int i = sStart; i < source.Length; i++) 36 { 37 if (IsMatchInternal(source, pattern, i + 1, pStart + 2)) return true; 38 } 39 } 40 else 41 { 42 for (int i = sStart; i < source.Length && source[i] == pattern[pStart]; i++) 43 { 44 if (IsMatchInternal(source, pattern, i + 1, pStart + 2)) return true; 45 } 46 } 47 } 48 else if (pattern[pStart + 1] == ‘+‘) 49 { 50 if (pattern[pStart] == ‘.‘) 51 { 52 for (int i = sStart; i < source.Length; i++) 53 { 54 if (IsMatchInternal(source, pattern, i + 1, pStart + 2)) return true; 55 } 56 } 57 else 58 { 59 for (int i = sStart; i < source.Length && source[i] == pattern[pStart]; i++) 60 { 61 if (IsMatchInternal(source, pattern, i + 1, pStart + 2)) return true; 62 } 63 } 64 } 65 else if (sStart < source.Length && (pattern[pStart] == ‘.‘ || pattern[pStart] == source[sStart])) 66 { 67 if (IsMatchInternal(source, pattern, sStart + 1, pStart + 1)) return true; 68 } 69 } 70 else if (sStart < source.Length && (pattern[pStart] == ‘.‘ || pattern[pStart] == source[sStart])) 71 { 72 if (IsMatchInternal(source, pattern, sStart + 1, pStart + 1)) return true; 73 } 74 75 return false; 76 } 77 }