第一题 import java.util.HashMap; import java.util.Map; import java.util.Scanner; public class Main { static Map<String, Integer> map = new HashMap<>(); public static void main(String[] args) throws Exception { Scanner sc = new Scanner(System.in); while (sc.hasNext()) { String s = sc.next(); System.out.println(removeCount(s)); } sc.close(); } public static int removeCount(String s) { if (s == null || s.isEmpty()) { return 1; } if (map.containsKey(s)) { return map.get(s); } int count = 0; String t = s.substring(1); for (int j = 0; j < t.length(); j++) { if (t.charAt(j) != ')') { continue; } String temp = t.substring(0, j) + t.substring(j + 1); if (isValid(temp)) { count += removeCount(temp); } } map.put(s, count); return count; } static boolean isValid(String s) { int count = 0; for (int i = 0; i < s.length(); i++) { char c = s.charAt(i); if (c == '(') { count++; } if (c == ')' && count-- == 0) { return false; } } return count == 0; } }