LeetCode 10. Regular Expression Matching

https://leetcode.com/problems/regular-expression-matching/description/

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

• 字符串匹配。最后一个样例中匹配是因为*可以是0次匹配，i.e. c0a2b。
• 递归法或者动态规划。

//
//  main.cpp
//  LeetCode
//
//  Created by Hao on 2017/3/16.
//  Copyright © 2017年 Hao. All rights reserved.
//

#include <iostream>
#include <string>
using namespace std;

class Solution {
public:
    bool isMatch(string s, string p) {
        return isMatch(s.c_str(), p.c_str());
    }

private:
    bool isMatch(const char *s, const char *p) {
        if (*p == '') return *s == '';
        
        // next char is not '*', must match the current char
        if (*(p + 1) != '*') {
            if ((*p == *s) || ((*p == '.') && (*s != '')))
                return isMatch(s + 1, p + 1);
            else
                return false;
        } else { // next char is '*'
            // '*' matches zero or more of the preceding element
            while ((*p == *s) || ((*p == '.') && (*s != ''))) {
                // check if the remaining string matches
                if (isMatch(s, p + 2))
                    return true;
                // move point
                s ++;
            }
            // next matching
            return isMatch(s, p + 2);
        }
    }
};

int main ()
{
    Solution testSolution;
    string sTest[] = {"aa", "a", "aa", "aa", "aaa", "aa", "aa", "a*", "aa", ".*", "ab", ".*", "aab", "c*a*b"};

    for (int i = 0; i < 7; i ++)
        cout << testSolution.isMatch(sTest[2 * i], sTest[2 * i + 1]) << endl;
    
    return 0;
}