【leetcode】Regular Expression Matching

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 class Solution {
 2 public:
 3     bool isMatch(const char *s, const char *p) {
 4
 5         if(s==NULL||p==NULL) return false;
 6         if(*p==‘\0‘&&*s==‘\0‘) return true;
 7         if(*p==‘\0‘&&*s!=‘\0‘) return false;
 8
 9         //如果模式串下一个字符为*
10         if(*(p+1)==‘*‘)
11         {
12             //循环比较当前字符与模式串字符是否相等
13             while((*s!=‘\0‘&&*p==‘.‘)||(*s==*p))
14             {
15                 //防止这种情况出现："aaa", "a*a"
16                 if(isMatch(s,p+2)) return true;
17                 s++;
18             }
19             return isMatch(s,p+2);
20         }
21         else if((*s!=‘\0‘&&*p==‘.‘)||*s==*p)
22         {
23             //如果当前元素相等，则开始匹配下一个元素
24             return isMatch(s+1,p+1);
25         }
26         return false;
27     }
28 };