poj1411
简单题
View Code
#include
<
iostream
>
#include
<
cstdio
>
#include
<
cstdlib
>
#include
<
cstring
>
#include
<
cmath
>
using
namespace
std;
#define
maxn 100005
bool
is
[maxn];
long
long
prm[maxn];
int
n, a, b, m, p, q;
int
getprm(
int
n)
{
int
i, j, k
=
0
;
int
s, e
=
(
int
) (sqrt(
0.0
+
n)
+
1
);
memset(
is
,
1
,
sizeof
(
is
));
prm[k
++
]
=
2
;
is
[
0
]
=
is
[
1
]
=
0
;
for
(i
=
4
; i
<
n; i
+=
2
)
is
[i]
=
0
;
for
(i
=
3
; i
<
e; i
+=
2
)
if
(
is
[i])
{
prm[k
++
]
=
i;
for
(s
=
i
*
2
, j
=
i
*
i; j
<
n; j
+=
s)
is
[j]
=
0
;
}
for
(; i
<
n; i
+=
2
)
if
(
is
[i])
prm[k
++
]
=
i;
return
k;
}
int
binarysearch()
{
int
l
=
0
;
int
r
=
n;
while
(l
<
r)
{
int
mid
=
(l
+
r)
/
2
+
((l
+
r)
&
1
);
if
(((
long
long
)prm[mid])
*
prm[mid]
<=
m)
l
=
mid;
else
r
=
mid
-
1
;
}
return
l;
}
void
work(
int
l,
int
r)
{
int
ans
=
prm[l]
*
prm[r];
q
=
p
=
prm[l];
while
(l
>=
0
)
{
if
(prm[l]
*
b
<
a
*
prm[r])
break
;
while
(r
<
n
-
1
&&
prm[l]
*
b
>=
a
*
prm[r
+
1
]
&&
prm[l]
*
prm[r
+
1
]
<=
m)
r
++
;
if
(ans
<
prm[l]
*
prm[r])
{
p
=
prm[l];
q
=
prm[r];
ans
=
prm[l]
*
prm[r];
}
l
--
;
}
printf(
"
%d %d\n
"
, p, q);
}
int
main()
{
//
freopen("t.txt", "r", stdin);
n
=
getprm(maxn
-
1
);
while
(scanf(
"
%d%d%d
"
,
&
m,
&
a,
&
b), m
|
a
|
b)
{
int
l, r;
l
=
r
=
binarysearch();
work(l, r);
}
return
0
;
}