題目描述:
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
題目解析:
代碼如下:
class Solution {
public:
bool isMach(const char *s, const char *p)
{
if(*s=='\0' && *p == '\0')
return true;
else if(*s != '\0' && *p == '\0')
return false;
// 如果*(p+1)是*,
if(*(p+1) == '*')
{
if(*p == *s || *p == '.' && *s != '\0')
// 有兩種情況,依次分別是:*代表和0個字符匹配,不起作用;*代表的已經和當前S匹配了。繼續看S的下一個,再看*到底可以代表幾個連續匹配
return isMach(s, p+2) || isMach(s+1, p);
return isMach(s, p+2);
}
// 如果s和p當前指向的值是一樣的;
else if(*s == *p || *p == '.' && *s != '\0') return isMach(s+1, p+1);
else
return false;
}
bool isMatch(string s, string p)
{
if(s.empty() && p.empty())
return true;
return isMach(s.c_str(), p.c_str());
}
};