question: public static void growPolygon ( float pts [ ] , int len , float amt ) { float [ ] c = centroid ( pts , len ) ; for ( int i = 0 ; i < len ; i += 2 ) { float vx = pts [ i ] - c [ 0 ] ; float vy = pts [ i + 1 ] - c [ 1 ] ; float norm = ( float ) Math . sqrt ( vx * vx + vy * vy ) ; pts [ i ] += amt * vx / norm ; pts [ i + 1 ] += amt * vy / norm ; } }
target:  Expand a polygon by adding the given distance along the line from the centroid of the polyong.