almost the same with Remove Duplicate, but to record the times of duplication while processing.

```
private static int dup = 2;
public int removeDuplicates(int[] nums) {
if (nums == null || nums.length == 0)
return 0;
int t = 0, i = 0, j = 0;
while (j < nums.length) {
if (t == dup) {
while (j < nums.length && nums[j] == nums[j - 1]) j ++;
if (j == nums.length) break;
}
nums[i] = nums[j];
if (i == 0 || nums[i] != nums[i - 1])
t = 1;
else t ++;
i ++; j ++;
}
return i;
}
```