Flatten 2D vector

class Vector2D:

    def __init__(self, vec: List[List[int]]):
        self.vec = vec
        # outer list
        self.row = 0
        # inner list
        self.col = 0

    def next(self) -> int:
        if not self.hasNext():
            return

        val = self.vec[self.row][self.col]
        self.col += 1

        # skip empty/exhausted rows right here
        while (self.row < len(self.vec)) and self.col >= len(self.vec[self.row]):
            self.row += 1
            self.col = 0

        return val


    def hasNext(self) -> bool:
        # skip empty rows
        while (self.row < len(self.vec)) and self.col >= len(self.vec[self.row]):
            self.row += 1
            self.col = 0
        if self.row < len(self.vec):
            return True
        else:
            return False


# Your Vector2D object will be instantiated and called as such:
# obj = Vector2D(vec)
# param_1 = obj.next()
# param_2 = obj.hasNext()