Efficiently determining whether a point is inside a triangle or on the edge : **How to determine whether a point lies inside of a triangle or on the edge efficiently, if possible with O(1) time.** 

Context:

- The plane is two dimensional
- Triangle is set according to three coordinate pairs `Coord(int x, int y)`
- The bounds for coordinates are: [-2,000,000 , 2,000,000 ]
- Triangle coordinates are assumed to be a valid triangle mesh
- Test point is also an integer.

Visual example:
[Image link][1]

Format example:

    Triangle a(Coord(50000,50000),Coord(-4000,2000), Coord(300000,150000));

                                   // Point  Result
    a.test_point( 60000,  45000)   // G      true
    a.test_point( 289500, 145500)  // F      true
    a.test_point( 292000, 146000)  // E      false
    a.test_point(-292000,-146000)  //-E      false
    a.test_point( 260000, 134000)  // D      true


  [1]: https://i.stack.imgur.com/FFhx1.png