【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

 

 class Solution {

 public:

     bool isMatch(const char *s, const char *p) {

         if(s==NULL||p==NULL) return false;

         if(*p=='\0'&&*s=='\0') return true;

         if(*p=='\0'&&*s!='\0') return false;

         //如果模式串下一个字符为*

         if(*(p+)=='*')

         {

             //循环比较当前字符与模式串字符是否相等

             while((*s!='\0'&&*p=='.')||(*s==*p))

             {

                 //防止这种情况出现："aaa", "a*a"

                 if(isMatch(s,p+)) return true;

                 s++;

             }

             return isMatch(s,p+);

         }

         else if((*s!='\0'&&*p=='.')||*s==*p)

         {

             //如果当前元素相等，则开始匹配下一个元素

             return isMatch(s+,p+);

         }

         return false;

     }

 };