Leetcode-Regular Expression Matching

#Leetcode

题目描述

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

AC代码

#include <iostream>
#include <cstdio>
#include <string>

using namespace std;

const int N = 10000;

bool isMatch(const char *s, const char *p)
{
    	if(*p == '\0')
    		return *s == '\0';
    	if(*(p+1) != '*')
    	{
    		if(*p == *s || (*p == '.' && *s != '\0'))
    			return isMatch(s+1, p+1);
    		else
    			return false;
    	}
    	else
    	{
    		while(*p == *s || (*p == '.' && *s != '\0'))
    		{
    			if(isMatch(s, p+2))
    				return true;
    			s++;
    		}
    		return isMatch(s, p+2);
    	}
}

int main()
{
    	char s[N], p[N];
    
    #ifndef ok
    	freopen("in3.in", "r", stdin);
    	freopen("std3.out", "w", stdout);
    #endif
    
    	while(cin>>s>>p)
    	{
    		if(isMatch(s, p))
    			cout<<"true"<<endl;
    		else
    			cout<<"false"<<endl;
    	}
    
    #ifndef ok
    	fclose(stdin);
    	fclose(stdout);
    #endif
    
    	return 0;
}