需求

2.代码

public class RegularExpressionMatching {public boolean isMatch(String s, String p) {if (p.isEmpty()) {return s.isEmpty();}boolean firstMatch =!s.isEmpty() && (s.charAt(0) == p.charAt(0) || p.charAt(0) == '.');if (p.length() >= 2 && p.charAt(1) == '*') {return isMatch(s, p.substring(2)) || (firstMatch && isMatch(s.substring(1), p));} else {return firstMatch && isMatch(s.substring(1), p.substring(1));}}public static void main(String[] args) {RegularExpressionMatching rem = new RegularExpressionMatching();String s = "aa";String p = "a";System.out.println(rem.isMatch(s, p)); // falses = "aa";p = "a*";System.out.println(rem.isMatch(s, p)); // trues = "ab";p = ".*";System.out.println(rem.isMatch(s, p)); // true}}