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") → false isMatch("aa","aa") → true isMatch("aaa","aa") → false isMatch("aa", "*") → true isMatch("aa", "a*") → true isMatch("ab", "?*") → true isMatch("aab", "c*a*b") → false
Analysis:
The difficulty of this problem is how to deal with '*' as it may match None or 1 or more chars.
Suppose we use a variable to record the position of '*' in string p, and we temporarily skip to the next non-'*' char. If that char in string p matches a char in string s, life is good - meaning that we could match the '*' with either None or multiple chars in string s; otherwise, we proceed the pointer in string s to seek for a matching char.
An example worth a million words. Suppose we have:
s="abcde", p="?**e*"
- compare 'a' with '?' ==> match, advance both pointers s & p
- see a '*', use variable star to record the star location, advance p, use variable ss to record s's pointer
- see another '*', update both p and star. Now s-->'b', p-->'e'
- variable star is not empty, advance both p and ss (and s), until we meet 'e' in string s
- 'e' matches 'e', advance both pointers, and now *s=='\0', we jump out of the while loop
- Finally, skip all left '*'s from string p. If we reach end of string p, return true; otherwise, return false;
Suppose we use a variable to record the position of '*' in string p, and we temporarily skip to the next non-'*' char. If that char in string p matches a char in string s, life is good - meaning that we could match the '*' with either None or multiple chars in string s; otherwise, we proceed the pointer in string s to seek for a matching char.
An example worth a million words. Suppose we have:
s="abcde", p="?**e*"
- compare 'a' with '?' ==> match, advance both pointers s & p
- see a '*', use variable star to record the star location, advance p, use variable ss to record s's pointer
- see another '*', update both p and star. Now s-->'b', p-->'e'
- variable star is not empty, advance both p and ss (and s), until we meet 'e' in string s
- 'e' matches 'e', advance both pointers, and now *s=='\0', we jump out of the while loop
- Finally, skip all left '*'s from string p. If we reach end of string p, return true; otherwise, return false;
Code:
class Solution { public: bool isMatch(const char *s, const char *p) { const char *star=NULL, *ss=s; while(*s!='\0') { if (*s==*p || *p=='?') { s++; p++; continue; } if (*p=='*') { star=p++; ss=s; continue; } if (star) { p=star+1; s=++ss; continue; } return false; } while (*p=='*') p++; return *p=='\0'; } };
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