somebody see a mistake?



#define MAXINT 2000000000
#include<stdio.h>
#include<math.h>
#include<stdlib.h>


typedef struct{
    int x,y;
    int ID;
    double ang;
}ponto_t;
ponto_t tb[10000];

int sort( const void *a, const void *b){
    ponto_t* ta = (ponto_t*)a;
    ponto_t* tb = (ponto_t*)b;
    if ((ta->x==0) && (ta->y==0)) return -1;
    if ((tb->x==0) && (tb->y==0)) return 1;
       return (ta->x*tb->y - tb->x*ta->y)>0?1:-1;
}


int main(){
    #ifndef ONLINE_JUDGE
        freopen("1207.in","r",stdin);
        freopen("1207.out","w",stdout);
    #endif
    int n,x=MAXINT,themin=0,k;
    scanf("%d",&n);


    for(k=0;k<n;k++){
        scanf("%d %d",&(tb[k].x),&(tb[k].y));
        tb[k].ID=k+1;
        if (tb[k].x<x){
            x=tb[k].x;
            themin=k;
        }
    }
    for(k=0;k<n;k++){
        tb[k].x-=tb[themin].x;
        tb[k].y-=tb[themin].y;
    }


    qsort(tb,n,sizeof(ponto_t),sort);

    printf("%d %d",tb[0].ID,tb[n/2].ID);

    return 0;
}

{My solution process by sorting the curve of point and geting the median
curve point ... thank}


const inp = '1207.in';
      maxn= 10005;
type  tdat = record xx,yy,id : longint; end;
var   fname              : text;
      dat                : array[1..maxn] of tdat;
      temp               : tdat;
      l,n,l2,min,m,mx,my,i : longint;
begin

     readln(n);
     min:=maxlongint;
     for l:=1 to n do
         begin
              readln(dat[l].xx,dat[l].yy);
              if dat[l].xx<min then
                 begin min:=dat[l].xx; m:=l; end;
              dat[l].id:=l;
         end;
     mx:=dat[m].xx; my:=dat[m].yy; i:=dat[m].id;
     for l:=1 to n-1 do
         for l2:=l+1 to n do
             if (my-dat[l2].yy)*(mx-dat[l].xx)
             >  (my-dat[l].yy) *(mx-dat[l2].xx) then
               begin
                    temp:=dat[l2];
                    dat[l2]:=dat[l];
                    dat[l]:=temp;
               end;
     for l:=1 to n do
         if (dat[l].xx=mx) and (dat[l].yy=my) then
            begin
                 if l>n div 2 then
                    writeln(i,' ',dat[n div 2].id)
                 else
                     writeln(i,' ',dat[(n div 2)+1].id);
                 halt;
            end;
end.

Here is my source.I am using VStudio 6.0 an dit is OK but...I got
Compilation Error. How to understand why and what to compile my
program with????

#include <stdio.h>
long ind,pom,n,x[10000],y[10000],ymin,i,j,xx,yy;
int pos[10000];
void main()
{
    scanf("%ld",&n);
    ymin=1000000000;
    for (i=0;i<n;i++)
    {
        scanf("%ld%ld",&x[i],&y[i]);
        pos[i]=i;
        if (ymin>y[i])
        {
            ind=i;
            ymin=y[i];
        }
    }
    pom=y[ind];
    y[ind]=y[n-1];
    y[n-1]=pom;
    pom=x[ind];
    x[ind]=x[n-1];
    x[n-1]=pom;
    xx=x[n-1];
    yy=y[n-1];
    pos[ind]=n-1;
    pos[n-1]=ind;
    for(i=0;i<n-1;i++)
        for(j=i+1;j<n;j++)
            if (((float)(x[i]-xx)*(float)(y[j]-yy))-
                ((float)(x[j]-xx)*(float)(y[i]-yy))>0)
            {
                pom=y[i];
                y[i]=y[j];
                y[j]=pom;
                pom=x[i];
                x[i]=x[j];
                x[j]=pom;
                pom=(long)pos[i];
                pos[i]=pos[j];
                pos[j]=(int)pom;
            }
printf("%d %d\n",pos[n-1]+1,pos[(int)((n/2)-1)]+1);
}

For a test case:
   if it should be output " a  b ", it also could be output
" b  a ",  which one is correct?
   for a test case,for example:
                4
                1 0
                0 1
                1 1
                2 2
  we could select not only 1 3, but also 3 4,
  which is the correct one ?

If N is a odd number,what's the output?
Do you have a input and the answer?

// heapsort the points (graham-like)

[code deleted]

Edited by moderator 24.11.2019 23:26