Gini impurity and information gain

Question

Let's consider this data set:
1 0 1 0 1 0 1 0
and this split:
1 0 1 0
1 0 1 0
What's the formula to calculate Gini impurity index of three sets?
And what's the formula to calculate information gain, since it is obviously 0, but Gini impurity index seems to be the same for all three sets?

Answer 1

https://towardsdatascience.com/gini-impurity-measure-dbd3878ead33