OJ Board

there is no critical input for this problem really bcoz u know all possible inputs!!

btw try the following input and output:

input:
1
10
100
1000
10000
100000

output:
(3, 5)
(107, 109)
(3821, 3823)
(79559, 79561)
(1260989, 1260991)
(18409199, 18409201)

hope it'll help

you'd better use VC.
TC wud never support such large array required for this problem.

thanx
-sohel

but you still can do it in this way:

create algorithm working with array i.e. 1000 elements and before sending solution create bigger array and send such solution. I did problems in this way in BC3.1 long time ago and it's work other method is using less memory consuming algorithms )

Dominik

But it may show output or memory limit exit.
Wt u think about it Michniewski?
i tried with such technic in another prob but didnt worked

I get TLE. Can anyone help me improve my algorithm?

Change ur algorithm.
Use the algorithm(for twin prime) to reduce unwanted calculation.
WIthout it its not possible to pass TLE

Jalal, I don't think so ....
If you run program under Windows / DOS you know how much memory you use ... Then If you increase limits, you know memory usage, i.e.

if your table has 1000 elements, and program use 100kB ram, then after change limit to 100000, than your program should use 10MB ram ....

And you know how is maximal limit for your arrays
Other way is counting memory self

Dominik

But how can I improve it?
I need to check all the odd to see if they are prime, shouldn't me?
And the algorithm of checking prime is standard...
Can anyone give me some hints?

Thanx Michniewski!
u r right.........
eric!
try with the following one

for(m= 6 ; m < x; m+=6)
if(prime(m-1) && prime(m+1))
printf("%ld %ld\n", m-1, m+1);

Thanks.
But I only know little about C++ and I can hardly understand your code.

Thanks, Jalal.
I change my algorithm and gradually get accepted.
Your post has given me some hint.

Hi,

This is my code, it is very simple but it finishes calculationes within the alloted time so thats just fine for me but im getting WA and i dont know why!!!!

[cpp]
#include <fstream.h>
#include <math.h>


/*Returns one if the number is prime, else it returns zero*/
int isPrime(int n)
{
int root = sqrt(n);
for(int i=3; i<root; i+=2)
if(n % i == 0)
return 0;

return 1;
}




void main()
{

long i=0,j;
long calc[100000][2]={3,5};
char *table = new char[18409201];
//ifstream cin;
//cin.open("texto.txt"); //just for testing


/*This is the core of the algorithm*/
for( i=3; i<=4290; i+=2)
if(isPrime(i))
for(j=i+i-1; j<18409201; j+=i)
table[j] = 0;

/*We now store ALL the twin primes*/
for(j=4,i=1; j<=18409201; j+=6)
if(table[j]!=0 && table[j+2]!=0)
{
calc[0]=j+1;
calc[1]=j+3;
i++;
}

/*Get the input and give the output*/
while(cin>>i)
cout<<"("<<calc[i-1][0]<<", "<<calc[i-1][1]<<")"<<endl;


}

[/cpp]


Could some of you guys please help me, I tested it with all the inputs that I culd imagine. is it something about the sapce ASCII32? omg so confused

can any of you guys tellme whats wrong with my code,
im getting WA

[cpp]

#include <fstream.h>
#include <math.h>


/*Returns one if the number is prime, else it returns zero*/
int isPrime(int n)
{
int root = sqrt(n);
for(int i=3; i<root; i+=2)
if(n % i == 0)
return 0;

return 1;
}


void main()
{

long i=0,j;
long calc[100000][2]={3,5};
char *table = new char[18409201];
//ifstream cin;
//cin.open("texto.txt"); //just for testing


/*This is the core of the algorithm*/
for( i=3; i<=4290; i+=2)
if(isPrime(i))
for(j=i+i-1; j<18409201; j+=i)
table[j] = 0;

/*We now store ALL the twin primes*/
for(j=4,i=1; j<=18409201; j+=6)
if(table[j]!=0 && table[j+2]!=0)
{
calc[0]=j+1;
calc[1]=j+3;
i++;
}

/*Get the input and give the output*/
while(cin>>i)
cout<<"("<<calc[i-1][0]<<", "<<calc[i-1][1]<<")"<<endl;


}
[/cpp]