The Missing Number

A list holds the whole numbers from 0 to n, each exactly once, except for one number that is missing. The numbers can be in any order, and the list has n items (one fewer than the full set).

Write missing_number(nums) that returns the missing number.

Examples

missing_number([3, 0, 1])                    # returns 2
missing_number([0, 1])                       # returns 2
missing_number([9, 6, 4, 2, 3, 5, 7, 0, 1])  # returns 8
missing_number([1])                          # returns 0

In the second example the list has 2 items, so the full set is 0, 1 and 2, and 2 is the one that is not there.

Constraints

• 0 <= len(nums) <= 10,000
• Every value is between 0 and len(nums), with no repeats

Note

An empty list means the full set was only 0, so the answer is 0.