```
public int combinationSum4(int[] nums, int target) {
if (nums == null || nums.length == 0 || target < 0) {
return 0;
}
int[] combs = new int[target + 1];
combs[0] = 1;
for (int i = 1; i <= target; i++) {
for (int j = 0; j < nums.length; j++) {
if (i - nums[j] >= 0) {
combs[i] += combs[i - nums[j]];
}
}
}
return combs[target];
}
```