What contest? On Feb 2, 12:41 pm, radha krishnan <radhakrishnance...@gmail.com> wrote: > I wonder U people discuss the solution during the contest ? > > > > On Wed, Feb 2, 2011 at 11:59 PM, Bhavesh agrawal <agr.bhav...@gmail.com> > wrote: > > if we just use hashing to store the different slope values .... > > > On Wed, Feb 2, 2011 at 7:45 PM, bittu <shashank7andr...@gmail.com> wrote: > > >> @above > > >> Use Simple Mathematics What is collinear Point...?? what is condition > >> of collinearity..?? thats it You have done > > >> Three or more points P1, P2, P3, ..., are said to be collinear if they > >> lie on a single straight line L similarly for N Points .. > > >> Let us start from the Very Basic Mathematical Approach > > >> Since any 2 points determine 1 line, take 2 of the points and find the > >> equation of the line drawn thru these 2 points. > >> Substitute the x and y of the either point into the equation and find > >> the y-intercept (b) > > >> Then, substitute the x and y of the 3rd point into the equation and > >> see if the both sides of the equation are =. > > >> (y2-y1) ÷ (x2 - x1) = slope > > >> y = slope * x + b > > >> Point # 1 = (6, 5)=p1 > >> Point # 2 = (10, 25)=p1 > >> Point # 3 = (12, 30)=p1 > >> Point # 4 = (12, 35)=p1 > > >> (y2 - y1) ÷ (x2 - x1) = slope > >> (25 - 5) ÷ (10 - 6) = slope > >> (20) ÷ (4) = slope > >> Slope = 5 > >> y = m * x + b > >> y = 5 * x + b > > >> Substitute the x and y of the point (6, 5) into the equation and find > >> the y-intercept (b) > >> y = 5 * x + b > >> 5 = 5 * 6 + b > >> 5 = 30 + b > >> b = -25 > >> y = 5 * x - 25 > >> . > >> Check your points > >> Point # 1 = (6, 5) > >> 5 = 5 * 6 - 25 > >> 5 = 30 - 25 OK > >> . > >> Point # 2 = (10, 25) > >> 25 = 5 * 10 - 25 > >> 25 = 5 * 10 - 25 OK > >> . > >> Then, substitute the x and y of the 3rd point into the equation and > >> see if the both sides of the equation are > >> Point # 3 = (12, 30) > >> . > >> y = 5 * x - 25 > >> 30 = 5 * 12 - 25 > >> 30 = 60 - 25 = 35 > >> Point # 3 = (12, 30) is not on the line > >> . > >> . > >> Point # 4 = (12, 35) > >> 35 = 5 * 12 - 25 > >> 35 = 60 - 25 =35 > >> Point # 4 = (12, 35) is on the line > > >> so we can p1,p2,p4 are Collinear > > >> 2nd Appraoch Used by Actual Geeks > > >> as we Two points are trivially collinear since two points determine a > >> line. > > >> Three points x_i=(xi,yi,zi) for i=1, 2, 3 are collinear if the ratios > >> of distances satisfy > > >> x2-x1:y2-y1:z2-z1=x3-x1:y3-y1:z3-z1 > > >> A slightly more notice that the area of a triangle determined by > >> three points will be zero iff they are collinear (including the > >> degenerate cases of two or all three points being concurrent), i.e., > > >> | x1 y1 1 | > >> | x2 y2 1 |=0 > >> | x3 y3 1 | > > >> or, in expanded form, > >> x1(y2-y3)+x2(y3-y1)+x3(y1-y2)=0 > > >> Still If You Have the Doubt Let Me Know & if Any found that anything > >> wrong in this..please write correct & efficient ways to do it. > > >> Thanks & Regards > >> Shashank ""The best way to escape from a problem is to solve it." > >> . > > >> . > > >> -- > >> You received this message because you are subscribed to the Google Groups > >> "Algorithm Geeks" group. > >> To post to this group, send email to algogeeks@googlegroups.com. > >> To unsubscribe from this group, send email to > >> algogeeks+unsubscr...@googlegroups.com. > >> For more options, visit this group at > >>http://groups.google.com/group/algogeeks?hl=en. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Algorithm Geeks" group. > > To post to this group, send email to algogeeks@googlegroups.com. > > To unsubscribe from this group, send email to > > algogeeks+unsubscr...@googlegroups.com. > > For more options, visit this group at > >http://groups.google.com/group/algogeeks?hl=en.- Hide quoted text - > > - Show quoted text -
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