leetcode Regular Expression Matching

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 boolean isMatch(String s, String p) {
 3         if (s.equals(p)) {
 4             return true;
 5         }
 6         
 7         int lenS=s.length();
 8         int lenP=p.length();
 9         if (lenP==0) {
10             return lenS==0;
11         }
12         if (lenP==1) {
13             if (p.equals(s)||(p.equals(".")&&lenS==1)) {
14                 return true;
15             }else {
16                 return false;
17             }
18         }
19         
20         if (p.charAt(1)!='*') {
21             if (lenS>0
22                     &&(s.charAt(0)==p.charAt(0)||p.charAt(0)=='.')) {
23                 return isMatch(s.substring(1), p.substring(1));
24             }
25             return false;
26         }else {
27             while (s.length()>0&&
28                     (s.charAt(0)==p.charAt(0)||p.charAt(0)=='.')) {
29                 if (isMatch(s, p.substring(2))) {
30                     return true;
31                 }
32                 s=s.substring(1);
33             }
34             return isMatch(s, p.substring(2));
35         }
36     }
37 }

 

posted @ 2014-12-25 22:02  birdhack  阅读(135)  评论(0)  编辑  收藏  举报