Regular Expression Matching--LeetCode

Regular Expression Matching

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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") → falseisMatch("aa","aa") → trueisMatch("aaa","aa") → falseisMatch("aa", "a*") → trueisMatch("aa", ".*") → trueisMatch("ab", ".*") → trueisMatch("aab", "c*a*b") → true

Solution：

使用递归算法

class Solution {public:    bool isMatch(string s, string p) {        if (p.length() == 0) return s.length() == 0;        if (p[1] == '*')        {            //isMatch("aab", "c*a*b") → true,返回isMatch("aab", "a*b")            //isMatch("aa", "a*") → true，返回isMatch("a", "a*")            //isMatch("aa", ".*") → true，返回isMatch("a", ".*")            //isMatch("a", ".*") → true，返回isMatch("", "")            return isMatch(s, p.substr(2)) || (s.length() != 0 && (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p));         }        else        {            if (s.length() != 0 && (s[0] == p[0] || p[0] == '.')) return isMatch(s.substr(1), p.substr(1));            return false;        }    }};