Given a list of integers values, your job is to return the sum of the values; however, if the same integer value appears multiple times in the list, you can only count it once in your sum.

For example:
```python
[ 1, 2, 3] ==> 6

[ 1, 3, 8, 1, 8] ==> 12

[ -1, -1, 5, 2, -7] ==> -1

[] ==> None
```

Good Luck!

Source: codewars | Difficulty: EASY
Tags: Fundamentals

Data structures

Starter code: def unique_sum(lst):
	

Solutions:
def unique_sum(lst):
	return sum(set(lst)) if lst else None


def unique_sum(lst):
	if lst:
		return sum(set(lst))


def unique_sum(lst):
	s = set(lst)
	return sum(s) if len(s) != 0 else None


unique_sum = lambda l: sum(set(l)) if l else None


def unique_sum(lst):
	new_lst = []
	for i in lst:
		if not i in new_lst:
			new_lst.append(i)
	return sum(new_lst) if lst else None


def unique_sum(lst):
	y = lambda x: sum(set(x))
	if len(lst) == 0:
		return None
	elif y(lst) == 0:
		return 0
	else:
		return y(lst)


def unique_sum(lst):
	if lst == []:
		return None
	else:
		s = set(lst)
		v = list(s)
		d = sum(v)
		return d