【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 };