# 44. 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") → 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
``````

Thoughts:

1. Keep track of last current input string position, current pattern string position and last asterisk (*) position.
2. O(n + m) without extra space
3. LeetCode: 44. Wildcard Matching, Wildcard Pattern Matching @ GeeksforGeeks and String Matching with Wildcards @ Hackerrank

Code (C):

`````` bool isMatch(const char *s, const char *p) {
const char* star=NULL;
const char* ss=s;
while (*s){
//advancing both pointers when (both characters match) or ('?' found in pattern)
//note that *p will not advance beyond its length
if ((*p=='?')||(*p==*s)){s++;p++;continue;}

// * found in pattern, track index of *, only advancing pattern pointer
if (*p=='*'){star=p++; ss=s;continue;}

//current characters didn't match, last pattern pointer was *, current pattern pointer is not *
if (star){ p = star+1; s=++ss;continue;}

//current pattern pointer is not star, last patter pointer was not *
//characters do not match
return false;
}

//check for remaining characters in pattern
while (*p=='*'){p++;}

return !*p;
}
``````

Code