1 import java.util.ArrayList;
 2 
 3 class Solution {
 4     public boolean judgePoint24(int[] nums) {
 5         ArrayList A = new ArrayList<Double>();
 6         for (int v: nums) A.add((double) v);
 7         return solve(A);
 8     }
 9     private boolean solve(ArrayList<Double> nums) {
10         if (nums.size() == 0) return false;
11         if (nums.size() == 1) return Math.abs(nums.get(0) - 24) < 1e-6;
12         for (int i = 0; i < nums.size(); i++) {
13             for (int j = 0; j < nums.size(); j++) {
14                 if (i != j) {
15                     ArrayList<Double> nums2 = new ArrayList<Double>();
16                     for (int k = 0; k < nums.size(); k++) if (k != i && k != j) {
17                         nums2.add(nums.get(k));
18                     }
19                     for (int k = 0; k < 4; k++) {
20                         if (k < 2 && j > i) continue;
21                         if (k == 0) nums2.add(nums.get(i) + nums.get(j));
22                         if (k == 1) nums2.add(nums.get(i) * nums.get(j));
23                         if (k == 2) nums2.add(nums.get(i) - nums.get(j));
24                         if (k == 3) {
25                             if (nums.get(j) != 0) {
26                                 nums2.add(nums.get(i) / nums.get(j));
27                             } else {
28                                 continue;
29                             }
30                         }
31                         if (solve(nums2)) return true;
32                         nums2.remove(nums2.size() - 1);
33                     }
34                 }
35             }
36         }
37         return false;
38     }
39 }