quacau
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Help me!!!
To me, it's extremely difficult(over 500 points)-sorry for that.
Please answer my question as soon as possible. Thank you!!!
I'm a pupil( 14 years old) who have a little experience in using pascal. And it's difficult for me to have to write a program by using pascal.
My problem is "closest pair in the plane problem". Using 2 algorithms: "divide and conquer" and "sweep the plane". Could you give me source code with a complete program.
To me, i will have to try my best to understand algorithms and your code.
Please answer my question as soon as possible. Thank you very much.!!!!
Please answer my question as soon as possible. Thank you!!!
I'm a pupil( 14 years old) who have a little experience in using pascal. And it's difficult for me to have to write a program by using pascal.
My problem is "closest pair in the plane problem". Using 2 algorithms: "divide and conquer" and "sweep the plane". Could you give me source code with a complete program.
To me, i will have to try my best to understand algorithms and your code.
Please answer my question as soon as possible. Thank you very much.!!!!
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ASKER
This program can't work correctly, if I have a mistake list( head^.next :=list) or i have some mistakes in function merge or function sort, thank you, i'll vote 500 points for you.
ASKER
Writeln( closest1.x); ( it can't display, means
new(head); head^.next:= list;
minresult := maxint;
sortx:= true; head^.next:=sort(head^.nex t,n);
sortx:= false; head^.next:= sort(head^.next,n); { implement algorithm}
have some problem, please check it for me. Thank you...
new(head); head^.next:= list;
minresult := maxint;
sortx:= true; head^.next:=sort(head^.nex
sortx:= false; head^.next:= sort(head^.next,n); { implement algorithm}
have some problem, please check it for me. Thank you...
ASKER
{ because i'm 14 years old pupil, please explain clearly, especially, this program seems to be correct but it can't run.}
{and i'd like to know how to use time function in pascal to display time of algorithm, when i use a large set of points, thank you}
program closest_pair; { divide and conquer}
uses crt,dos,overlay;
type
point = record
x: real;
y: real;
end;
link = ^node;
node = record
p: point;
next: link;
end;
var
keeptrack: link; { i'll use it to keep track of my list}
list,head: link; {i'll use list to input a set of points}
first: link;
minresult: real;
closest1,closest2: point; {current closest pair, they can be updated}
sortx: boolean; {sortx = false -> sort y}
n,v: integer; {n points}
function merge(list1,list2 :link) : link;
var list12: link;
addlist :boolean;
begin
list12:= keeptrack ; {it seems to be unlimited loop, really difficult or i have a wrong list that declares in the main program }
repeat
if sortx = true then addlist:= list1^.p.x < list2^.p.x
else addlist:= list1^.p.y < list2^.p.y ;
if addlist then begin list12^.next := list1; list12:= list1; list1 := list1^.next end
else begin list12^.next := list2; list12:=list2; list2 := list2^.next end
until list12 = keeptrack;
merge := keeptrack^.next;
keeptrack^.next := keeptrack;
end;
procedure check(p1,p2: point); { it's easy, i got it}
var distance : real;
begin
if (p1.y <> keeptrack^.p.y) and (p2.y<> keeptrack^.p.y) then
begin distance := sqrt((p1.x -p2.x)*(p1.x -p2.x) + (p1.y -p2.y)*(p1.y - p2.y));
if distance < minresult then
begin minresult:= distance;
closest1:= p1;
closest2:= p2;
end;
end;
end;
function sort(c: link; n: integer):link;
var a,b: link;
i: integer;
middle: real;
p1,p2,p3,p4: point;
begin
if c^.next = keeptrack then sort:= c else
begin a := c;
for i:= 2 to (n div 2) do c:= c^.next;
b:= c^.next;
c^.next := keeptrack;
if sortx = false then middle := b^.p.x;
c := merge(sort(a, n div 2), sort(b,n-(n div 2)));
sort := c;
if sortx = false then
begin
a:= c; p1:=keeptrack^.p; p2:=keeptrack^.p; p3:= keeptrack^.p; p4:= keeptrack^.p;
repeat
if abs(a^.p.x - middle) < minresult then
begin check(a^.p,p1);
check(a^.p,p2);
check(a^.p,p3);
check(a^.p,p4);
p1:=p2; p2:=p3; p3:=p4; p4:=a^.p;
end;
a:= a^.next;
until a=keeptrack ;
end;
end;
end;
begin { please check this for me,do i have s mistakes}
new(keeptrack);
keeptrack^.next:=keeptrack
keeptrack^.p.x:= maxint;
keeptrack^.p.y:= maxint;
writeln('how many points are there on the plane: ????');
readln(n);
list := nil;
for v:=1 to n do begin
new(first);
first^.p.x := random(1000);
first^.p.y := random(1000);
first^.next := list;
list := first;
end;
new(head); head^.next:= list;
minresult := maxint;
sortx:= true; head^.next:=sort(head^.nex
sortx:= false; head^.next:= sort(head^.next,n);
writeln(closest1.x); { the problem is not important anymore}
readln;
end.