How Many Triangles?

Solves the "how many triangles in this shape?" types of riddles

Example

Usages

The application takes an input of lines made up of indices of nodes (lines intersections) in the shape.

Mark each node with a unique index and create a Line from the indices of each actual (full) line in the shape:

Line[] example =
{
    //Horizontal lines (-):
    new Line(){ 2, 3 }),
    new Line(){ 4, 5, 6 }),
    new Line(){ 7, 8, 9, 10 }),
    new Line(){ 11, 12, 13, 14, 15 }),
    //Diagonal lines (/)
    new Line(){ 1, 2 , 4 , 7 , 11  }),
    new Line(){ 3, 5 , 8 , 12 }),
    new Line(){ 6, 9 , 13 }),
    new Line(){ 10, 14 }),
    //Diagonal lines (\)
    new Line(){ 1, 3 , 6 , 10 , 15  }),
    new Line(){ 2, 5 , 9 , 14 }),
    new Line(){ 4, 8 , 13 }),
    new Line(){ 7, 12 }),
};

Output

Running the above example gives the following result: