匹配

The basic idea is to check and advance two pointers in two strings correspondingly if satisfying specific condition. And 
the trick part is the attempting backtracking method for '*' matching, which can be checked out in the code. Thanks for 
this great idea from Yu and pandora.

public boolean isMatch(String str, String pattern) {        
    int s = 0, p = 0, pStar = -1, sMatchStar = 0; // s is the pointer index of str; p is the pointer index of pattern.
    while (s < str.length()){ 
        // Advancing both pointers: if current pointer of pattern is '?', or current two pointers sMatchStar
        if (p < pattern.length() && (pattern.charAt(p) =='?' || pattern.charAt(p)==str.charAt(s))){
            s++;
            p++;
        } 
        else if (p < pattern.length() && pattern.charAt(p) == '*') {
            // Only advancing pattern pointer, and track index of '*': if current pointer of pattern is '*'
            pStar = p; 
            sMatchStar = s;
            p++;
        } 
        else if (pStar != -1){// Only advancing string pattern : if last pattern was '*'
            p = pStar + 1;  // If current characters didn't match, try to backtrack p to '*' + 1
            sMatchStar++;     
            s = sMatchStar; // Backtrack s to last index matching '*' + 1
        } 
        // Characters didn't sMatchStar: 1) Current two pointers didn't sMatchStar; 2) No '?' found; 3) No '*' found.
        else return false;
    }

    // Check the remaining characters in pattern: only advancing with '*'
    while (p < pattern.length() && pattern.charAt(p) == '*')
        p++;
    // Characters only sMatchStar if the pattern reaches its end.
    return p == pattern.length();  
}