Leetcode-10. 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
思路:DP
1.如果p结束的时候,s必须结束,否则false;
2.*(p+1)=='*'的情况:*p为'.'或者*p==*s 循环到s的结尾;
3.*(p+1)不是'*'的情况,逐字检查就好。
AC code:
bool isMatch(char* s, char* p) { if(s==NULL||p==NULL) return false; if(*p=='\0') return *s=='\0'; if(*(p+1)=='*') { while(*s!='\0'&&*p=='.'||*s==*p) { if(isMatch(s,p+2)) return true; s++; } return isMatch(s,p+2); } else if((*s!='\0'&&*p=='.')||*s==*p) { return isMatch(s+1,p+1); } return false; }