mexFunction.py

# You've just started to study impartial games, and came across an interesting theory. The theory is quite complicated, but it can be narrowed down to the following statements: solutions to all such games can be found with the mex function. Mex is an abbreviation of minimum excludant: for the given set s it finds the minimum non-negative integer that is not present in s.

# You don't yet know how to implement such a function efficiently, so would like to create a simplified version. For the given set s and given an upperBound, implement a function that will find its mex if it's smaller than upperBound or return upperBound instead.

# Hint: for loops also have an else clause which executes when the loop completes normally, i.e. without encountering any breaks
def mexFunction(s, upperBound):
    found = -1
    for i in range(upperBound):
        if not i in s:
            found = i
            break
    else:
        found = upperBound

    return found