【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+1)=='*')
        {
            //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+2)) return true;
                s++;
            }
            return isMatch(s,p+2);
        }
        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+1,p+1);
        }
        return false;
    }
};