package offer;
/*
 * 字串匹配
 * "."匹配任意一個字元
 * "*"表示前面的字元出現任意次
 */
public class Match {
    public static void main(String[] args) {
        String str = "aaa";
        String pattern = "b*aaaa*a*a*a*.*";
        System.out.println(match(str, 0, pattern, 0));
    }

    private static boolean match(String str
 
, int strIndex, String pattern, int patternIndex) {
        //出口1 ：兩個字串都到達了結尾，說明匹配成功，返回true
        if (strIndex >= str.length() && patternIndex >= pattern.length()) {
            return true;
        }
        //出口2 ：模式串達到了結尾，說明匹配失敗，返回false
        if (strIndex != str.length() && patternIndex >= pattern.length()) {
            return
 
 false;
        }

        //若下一個字元為'*'
        if (patternIndex + 1 < pattern.length() && pattern.charAt(patternIndex + 1) == '*') {
            if(strIndex >= str.length()){  
                //若匹配串已經結束  
                return match(str, strIndex, pattern, patternIndex + 2);
            } else
 
 {
                if (str.charAt(strIndex) == pattern.charAt(patternIndex) || (pattern.charAt(patternIndex) == '.' && strIndex != str.length()) ) {
                    return match(str, strIndex, pattern, patternIndex + 2)
                            ||match(str, strIndex + 1, pattern, patternIndex + 2)
                            ||match(str, strIndex + 1, pattern, patternIndex);
                } else {
                    return match(str, strIndex, pattern, patternIndex + 2);
                }
            }
        }

        //若當前字元為'.'
        if(strIndex >= str.length()){ 
            //若匹配串已經結束  
            return false;
        } else{
            if (str.charAt(strIndex) == pattern.charAt(patternIndex) || pattern.charAt(patternIndex) == '.') {
                return match(str, strIndex + 1, pattern, patternIndex + 1);
            }
        }

        return false;
    }
}