Problem Description
A message from humans to extraterrestrial intelligence was
sent through the Arecibo radio telescope in Puerto Rico on the
afternoon of Saturday November 16, 1974. The message consisted of
1679 bits and was meant to be translated to a rectangular picture
with 23 * 73 pixels. Since both 23 and 73 are prime numbers, 23 *
73 is the unique possible size of the translated rectangular
picture each edge of which is longer than 1 pixel. Of course, there
was no guarantee that the receivers would try to translate the
message to a rectangular picture. Even if they would, they might
put the pixels into the rectangle incorrectly. The senders of the
Arecibo message were optimistic.
We are planning a similar project. Your task in the project is
to find the most suitable width and height of the translated
rectangular picture. The term "most suitable" is defined as
follows. An integer m greater than 4 is given. A positive fraction
a / b less than or equal to 1 is also given. The area of the
picture should not be greater than m. Both of the width and the
height of the translated picture should be prime numbers. The ratio
of the width to the height should not be less than a / b nor
greater than 1. You should maximize the area of the picture under
these constraints.
In other words, you will receive an integer m and a fraction a
/ b. It holds that m > 4 and 0 < a / b < 1. You should
find the pair of prime numbers p, q such that pq <= m and a / b
<= p / q <= 1, and furthermore, the product pq takes the
maximum value among such pairs of two prime numbers. You should
report p and q as the "most suitable" width and height of the
translated picture.
Input
The input is a sequence of at most 2000 triplets of positive
integers, delimited by a space character in between. Each line
contains a single triplet. The sequence is followed by a triplet of
zeros, 0 0 0, which indicated the end of the input and should not
be treated as data to be processed.
The integers of each input triplet are the integer m, the
numerator a, and the denominator b described above, in this order.
You may assume 4 < m <= 100000 and 1 <= a <= b <=
1000.
Output
The output is a sequence of pairs of positive integers. The
i-th output pair corresponds to the i-th input triplet. The
integers of each output pair are the width p and the height q
described above, in this order.
Each output line contains a single pair. A space character is
put between the integers as a delimiter. No other characters should
appear in the output.
Sample Input
5 1 2
99999 999 999
1680 5 16
1970 1 1
2002 4 11
0 0 0
Sample Output
2 2
313 313
23 73
43 43
37 53
题目比较简单，算是水题吧
#include
#include
#include
using namespace std;
int prime(int x)
{
int flag=1;
if(x==1)
flag=0;
if(x==2)
flag=1;
else
for(int i=2;i<=sqrt(x);i++)
{ flag=1;
if(x%i==0)
}
if(flag)
return 1;
else
return 0;
}
int main()
{
int m,j;
int a,b;
int flag=0;
while(scanf("%d%d%d",&m,&a,&b),m,a,b)
{ flag=0;
float s=1.0*a/b;
for(int i=m;i>=4;i--)
if(!prime(i))
{
for(j=2;j<=sqrt(i);j++)
{
if(i%j==0)
{
if(prime(j)&&prime(i/j)&&((1.0*j/(i/j))>=s)&&((1.0*j/(i/j))<=1))
}
}
if(flag)
}
return 0;
}