poj1328为什么我狂wa？

[sunsnowdrop]

#include<iostream>
#include<cmath>
using namespace std;

struct seg
{
double left , right;
}p[1000];

int n , d , maxr , cnt , c = 1 , x , y;
bool imp;

int myCom ( const void * e1 , const void * e2 )
{
seg * p1 = ( seg * ) e1 ;
seg * p2 = ( seg * ) e2 ;
if ( p1->left != p2->left )
return (p1->left - p2->left)>0?1:-1 ;
else
return (p1->right - p2->right)>0 ? 1:-1;
}

int main()
{
while ( scanf("%d %d" , &n , &d ))
{
if ( n== 0 && d== 0 )
break;

imp = false; //判断是否可能

for ( int i = 0 ; i < n ; ++ i )
{
scanf("%d %d" , &x , &y);
if ( abs(y) > abs(d) )
imp = true;
p[i].left = x - sqrt(double(d*d-y*y));
p[i].right = x + sqrt(double(d*d-y*y));
}

if ( imp )
printf("Case %d: -1\n" , c++);

qsort( p , n , sizeof(seg) , myCom);

cnt = 1 ;
maxr = p[0].right ;

for ( int i = 1 ; i < n ; ++ i )
{
if ( p[i].left > maxr )
{
++ cnt;
maxr = p[i].right ;
}
else if ( p[i].right < maxr )
maxr = p[i].right ;
}

printf("Case %d: %d\n" , c++ , cnt );
}
return 0;
}

[黄舒颖 咸丫蛋]

[Quote=引用楼主 sunsnowdrop 的帖子:]
#include <iostream>
#include <cmath>
using namespace std;

struct seg
{
double left , right;
}p[1000];

int n , d , maxr , cnt , c = 1 , x , y;
bool imp;

int myCom ( const void * e1 , const void * e2 )
{
seg * p1 = ( seg * ) e1 ;
seg * p2 = ( seg * ) e2 ;
if ( p1->left != p2->left )
return (p1->left - p2->left)>0?1:-1 ;
else
return (p1->right - p2->right)>0 ? 1:-1;
}

int main()
{
while ( scanf("%d %d" , &n , &d ))
{
if ( n== 0 && d== 0 )
break;

imp = false; //判断是否可能

for ( int i = 0 ; i < n ; ++ i )
{
scanf("%d %d" , &x , &y);

if ( abs(y) > abs(d) ) //漏了一种情况，如果d<0时也可以是impossible，但你没有能cover住
imp = true;
p[i].left = x - sqrt(double(d*d-y*y));
p[i].right = x + sqrt(double(d*d-y*y));
}

if ( imp )
printf("Case %d: -1\n" , c++);

qsort( p , n , sizeof(seg) , myCom);

cnt = 1 ;
maxr = p[0].right ;

for ( int i = 1 ; i < n ; ++ i )
{
if ( p[i].left > maxr )
{
++ cnt;
maxr = p[i].right ;
}
else if ( p[i].right < maxr )
maxr = p[i].right ;
}

printf("Case %d: %d\n" , c++ , cnt );
}
return 0;
}[/Quote]

[adfas]

记得是道贪心
这题靠RP