LeetCode(10) Regular Expression Matching解题报告

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正则式匹配

问题:

‘.’ Matches any single character.
‘*’ Matches zero or more of the preceding element.
The matching should cover the entire input string (not partial).
The function prototype should be:
bool isMatch(const char *s, const char *p)

翻译:

‘.’ 匹配任何单个字符
‘*’ 匹配0个或者多个元素
应该匹配整个字符串而不是部分匹配
方法原型:
bool isMatch(const char *s, const char *p)

示例:

isMatch(“aa”,”a”) → false
isMatch(“aa”,”aa”) → true
isMatch(“aaa”,”aa”) → false
isMatch(“aa”, “a*”) → true
isMatch(“aa”, “.*”) → true
isMatch(“ab”, “.*”) → true
isMatch(“aab”, “c*a*b”) → true

解题方案：

public boolean isMatch(String text, String pattern) {
    if (pattern.isEmpty())
        return text.isEmpty();
    boolean first_match = (!text.isEmpty() && (pattern.charAt(0) == text.charAt(0) || pattern.charAt(0) == '.'));

    if (pattern.length() >= 2 && pattern.charAt(1) == '*') {
        return (isMatch(text, pattern.substring(2)) || (first_match && isMatch(text.substring(1), pattern)));
    } else {
        return first_match && isMatch(text.substring(1), pattern.substring(1));
    }
}