24-point Game Dynamic Programming solution (Java)

Algorithm principle reference Programming Beauty 1.16 Chapter Solution 2:

Below is the Java source code: The child problem is s[i] u= Fork (f (x), F (i));

Import Java.util.HashMap;
Import Java.util.HashSet;
Import Java.util.Map;
Import Java.util.Scanner;

Import Java.util.Set;
	Class elem{public double res;
	public String info;
		Public Elem (double r,string i) {res = R;
	info = i;
	} public class Calculateanswer {private final int N = 4;
	Private final int res = 24;
	Private int[] A;
	Private Map<integer, set<elem>> Map;
	
	Private set<string> answers;
		Public Calculateanswer (int[] a) {a = A;
		Map = new Hashmap<integer, set<elem>> ();

	Answers = new hashset<string> ();
			public void Run () {for (int i=0;i< (1<<n); i++) {set<elem> Set = new hashset<elem> ();
		Map.put (I,set);
			for (int i=0;i<n;i++) {Elem e = new Elem (a[i), a[i]+ "");
			set<elem> set = new hashset<elem> ();
			Set.add (e);
		Map.put (1<<i, set);
		for (int i = 1; i < (1 << N); i++) {fork (i);
		} set<elem> Mset = Map.get ((1<<n)-1); for (ElemE:mset) {if (e.res==res) {answers.add (e.info);
		} if (Answers.size () ==0) {System.out.println ("no solution");
			else {for (String s:answers) System.out.println (s);
		SYSTEM.OUT.PRINTLN ("Total" +answers.size () + "solution");
		} public set<elem> fork (int m) {set<elem> Mset = Map.get (m);
		if (Mset.size () >0) return mset;
					else {for (int x = 1; x <= m x + +) {if (x&m) ==x) {set<elem> S1 = fork (x);
					set<elem> s2 = fork (m-x);
							for (Elem e1:s1) {for (Elem e2:s2) {String str = "(" +e1.info+ "+" +e2.info+ ")";
							
							Mset.add (New Elem (E1.res+e2.res, str));
							str = "(" + e1.info+ "-" +e2.info+ ")";
							
							Mset.add (New Elem (E1.res-e2.res, str));
							str = "(" + e2.info+ "-" +e1.info+ ")";
							
							Mset.add (New Elem (E2.res-e1.res, str));
							str = "(" + e1.info+ "*" +e2.info+ ")";
							
							Mset.add (New Elem (E1.res*e2.res, str)); if (e1.res!=0) {str = "(" + e2.info+ "/"+e1.info+") ";
							Mset.add (New Elem (E2.res/e1.res, str));
								} if (e2.res!=0) {str = "(" + e1.info+ "/" +e2.info+ ")";
							Mset.add (New Elem (E1.res/e2.res, str));
		}}} return mset;
		} public static void Main (string[] args) {int[] a = new int[4];
		Scanner sc = new Scanner (system.in);
		for (int i = 0;i<4;i++) {A[i] = Sc.nextint ();
		} calculateanswer cal = new Calculateanswer (a);
		Cal.run ();
	Sc.close ();
 }
}