1 class Solution {
 2     public boolean isPossible(int[] nums) {
 3         Counter count = new Counter();
 4         Counter tails = new Counter();
 5         for (int x: nums) count.add(x, 1);
 6 
 7         for (int x: nums) {
 8             if (count.get(x) == 0) {
 9                 continue;
10             } else if (tails.get(x) > 0) {
11                 tails.add(x, -1);
12                 tails.add(x+1, 1);
13             } else if (count.get(x+1) > 0 && count.get(x+2) > 0) {
14                 count.add(x+1, -1);
15                 count.add(x+2, -1);
16                 tails.add(x+3, 1);
17             } else {
18                 return false;
19             }
20             count.add(x, -1);
21         }
22         return true;
23     }
24 }
25 
26 class Counter extends HashMap<Integer, Integer> {
27     public int get(int k) {
28         return containsKey(k) ? super.get(k) : 0;
29     }
30 
31     public void add(int k, int v) {
32         put(k, get(k) + v);
33     }
34 }