How to find whether the point lies between these points

Question

I have been trying to create a curve and i've already created it . but the thing is if i add a point it will be added to the array[last point -1] , but if i add a point between the first and second point the curve takes it as the last point -1 which is my coding anyway, I need to find where i shoulkd add , the index of the curve

The above imnage is an example , here i have a curve with three points , the point's are numbered so that you can see how the points are stored in the array , I am going to add the purple point to th array but i need to know which index i should paste , please help

Answer 1

I just created new seperate sprites for each of the curves and found the points when the click event is dispatched , thanks for your suggestions.