### Question

Given a polygon and a point ‘p’, find if ‘p’ lies inside the polygon or not. The points lying on the border are considered inside.

### Solution

Prerequisite reading: **[Question] Check if two line segments intersect**.

Suggested by G4G, this is a simple idea to check:

Draw a horizontal line to the right of each point and extend it to infinity

Count the number of times the line intersects with polygon edges.

A point is inside the polygon if either count of intersections is odd or point lies on an edge of polygon.

Note the special case of point ‘g’.