poj1118

简单题

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      #include 
    
      <
    
      iostream
    
      >
    
      
#include 
    
      <
    
      cstdio
    
      >
    
      
#include 
    
      <
    
      cstdlib
    
      >
    
      
#include 
    
      <
    
      cstring
    
      >
    
      
#include 
    
      <
    
      cmath
    
      >
    
      
#include 
    
      <
    
      algorithm
    
      >
    
      

    
      using
    
       
    
      namespace
    
       std;


    
      #define
    
       maxn 705
    
      

    
      #define
    
       eps 10E-9
    
      


    
      struct
    
       Point
{
 
    
      int
    
       x, y;
} point[maxn];


    
      struct
    
       Node
{
 
    
      double
    
       k;
 
    
      int
    
       a, b;
} f[maxn 
    
      *
    
       maxn];


    
      int
    
       n, ncount;

    
      double
    
       inf;


    
      bool
    
       
    
      operator
    
       
    
      <
    
      (
    
      const
    
       Point 
    
      &
    
      a, 
    
      const
    
       Point 
    
      &
    
      b)
{
 
    
      return
    
       (a.x 
    
      ==
    
       b.x 
    
      &&
    
       a.y 
    
      <
    
       b.y) 
    
      ||
    
       a.x 
    
      <
    
       b.x;
}


    
      bool
    
       
    
      operator
    
       
    
      <
    
      (
    
      const
    
       Node 
    
      &
    
      a, 
    
      const
    
       Node 
    
      &
    
      b)
{
 
    
      if
    
       (abs(a.k 
    
      -
    
       b.k) 
    
      >
    
       eps)
 
    
      return
    
       a.k 
    
      <
    
       b.k;
 
    
      return
    
       (a.a 
    
      ==
    
       b.a 
    
      &&
    
       a.b 
    
      <
    
       b.b) 
    
      ||
    
       a.a 
    
      <
    
       b.a;
}


    
      double
    
       cal(Point 
    
      &
    
      a, Point 
    
      &
    
      b)
{
 
    
      if
    
       (a.x 
    
      ==
    
       b.x)
 
    
      return
    
       inf;
 
    
      return
    
       (b.y 
    
      -
    
       a.y) 
    
      *
    
       
    
      1.0
    
       
    
      /
    
       (b.x 
    
      -
    
       a.x);
}


    
      int
    
       main()
{
 inf 
    
      =
    
       
    
      1.79769e+308
    
      ;
 
    
      //
    
      freopen("t.txt", "r", stdin);
    
      

    
       
    
      while
    
       (scanf(
    
      "
    
      %d
    
      "
    
      , 
    
      &
    
      n), n)
 {
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 scanf(
    
      "
    
      %d%d
    
      "
    
      , 
    
      &
    
      point[i].x, 
    
      &
    
      point[i].y);
 sort(point, point 
    
      +
    
       n);
 ncount 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      0
    
      ; i 
    
      <
    
       n; i
    
      ++
    
      )
 
    
      for
    
       (
    
      int
    
       j 
    
      =
    
       i 
    
      +
    
       
    
      1
    
      ; j 
    
      <
    
       n; j
    
      ++
    
      )
 {
 f[ncount].a 
    
      =
    
       i;
 f[ncount].b 
    
      =
    
       j;
 f[ncount].k 
    
      =
    
       cal(point[i], point[j]);
 ncount
    
      ++
    
      ;
 }
 sort(f, f 
    
      +
    
       ncount);
 
    
      int
    
       len 
    
      =
    
       
    
      1
    
      ;
 
    
      int
    
       ans 
    
      =
    
       
    
      0
    
      ;
 
    
      for
    
       (
    
      int
    
       i 
    
      =
    
       
    
      1
    
      ; i 
    
      <
    
       ncount; i
    
      ++
    
      )
 {
 
    
      if
    
       (f[i].a 
    
      ==
    
       f[i 
    
      -
    
       len].a 
    
      &&
    
       abs(f[i].k 
    
      -
    
       f[i 
    
      -
    
       len].k) 
    
      <
    
       eps)
 len
    
      ++
    
      ;
 
    
      else
    
      
 {
 ans 
    
      =
    
       max(ans, len);
 len 
    
      =
    
       
    
      1
    
      ;
 }
 }
 printf(
    
      "
    
      %d\n
    
      "
    
      , ans 
    
      +
    
       
    
      1
    
      );
 }
 
    
      return
    
       
    
      0
    
      ;
}