JZ52 正则表达式匹配

https://www.nowcoder.com/practice/28970c15befb4ff3a264189087b99ad4

第一次解

基本就是放弃了....

public class Solution {
    /**
     * @param str string字符串 
     * @param pattern string字符串 
     * @return bool布尔型
     */
    public boolean match (String str, String pattern) {
        // 不想做这题
        return Pattern.matches(pattern, str);
    }
}

第二次解

这题真的很难！！等以后重写

    public boolean match(String str, String pattern) {
// write code here
        if (str == null || pattern == null) return false;
        int strIndex = 0;
        int patternIndex = 0;
        char[] ch1 = str.toCharArray();
        char[] ch2 = pattern.toCharArray();
        return matchCore(ch1, ch2, strIndex, patternIndex);
    }

    public boolean matchCore(char[] str, char[] pattern, int strIndex, int patternIndex) {
        if (strIndex == str.length && patternIndex == pattern.length) {
            return true;
        }

        if (strIndex != str.length && patternIndex == pattern.length) {
            return false;
        }
        // 当下一个字符为 * 的情况
        if (patternIndex + 1 < pattern.length && pattern[patternIndex + 1] == '*') {

            if ((strIndex != str.length && pattern[patternIndex] == str[strIndex]) ||
                    (pattern[patternIndex] == '.' && strIndex != str.length)) {
                return matchCore(str, pattern, strIndex, patternIndex + 2) ||
                        matchCore(str, pattern, strIndex + 1, patternIndex + 2) ||
                        matchCore(str, pattern, strIndex + 1, patternIndex);
            } else {
                return matchCore(str, pattern, strIndex, patternIndex + 2);
            }
        }

        // 匹配成功则正常的判断下一个子串
        if ((strIndex != str.length && pattern[patternIndex] == str[strIndex]) || (pattern[patternIndex] == '.' && strIndex != str.length)) {
            return matchCore(str, pattern, strIndex + 1, patternIndex + 1);
        }

        return false;
    }