leetcode之通配符

Wildcard Matching

Implement wildcard pattern matching with support for '?' and '*'.

'?' Matches any single character.'*' Matches any sequence of characters (including the empty sequence).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", "*") → trueisMatch("aa", "a*") → trueisMatch("ab", "?*") → trueisMatch("aab", "c*a*b") → false

思路：本题是正常的通配符匹配，可以使用循环，也可以使用递归。使用循环时，每次遇到'*'时，要记录他的位置，这样当匹配失败时，返回到该位置重新匹配。

class Solution {public:    bool isMatch(const char *s, const char *p) {    const char* sBegin = NULL,*pBegin = NULL;    while(*s)    {    if(*s == *p || *p == '?')    {    ++s;    ++p;    }    else if(*p == '*')    {    pBegin = p;//记录通配符的位置    sBegin = s;    ++p;    }    else if(pBegin != NULL)    {    p = pBegin + 1;//重通配符的下一个字符开始    ++sBegin;//每次多统配一个    s = sBegin;    }    else return false;    }    while(*p == '*')++p;    return (*p == '\0');    }};

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

思路：本题和上面不同之处在于，此时的通配符'*'和它前面的字符看成一个整体，它们两个代表0到多个第一个字符，而不是任一个字符。所以，当下一个字符是'*'时，如果当前字符相等，则反复跳过当前字符去匹配'*'后面的字符，如果不相等，则直接匹配'*'后面的字符。

class Solution {public:    bool isMatch(const char *s, const char *p) {    if(*p == '\0')return *s == '\0';    if(*(p+1) != '*')    {    if(*s != '\0' && (*s == *p || *p == '.'))return isMatch(s+1,p+1);    }    else     {    //s向后移动0、1、2……分别和p+2进行匹配    while(*s != '\0' && (*s == *p || *p == '.'))    {    if(isMatch(s,p+2))return true;    ++s;    }    return isMatch(s,p+2);    }    return false;    }};