Prime Generator Problem in C++

[ap00rva]

Hi All,
I have submitted solution to Prime Generator Problem. I have run it in Visual Studio and gives me correct output for small or large numbers.

Still I am getting wrong answer when I submit the code:

//2. Prime Generator
//Problem code: PRIME1
#include "iostream"
#include <stdio.h>
#include <math.h>
void find_prime_fast(unsigned long m, unsigned long n)
{
	unsigned long *arr = new(std::nothrow) unsigned long[n+1];
	if(arr==NULL)
	{	
		std::cout<<"Memory could not be allocated";
		delete [] arr;
		return;
	}
    for (unsigned long i=0;i<n;i++)
{
	*(arr+i)=i;
}
unsigned long a=sqrt((long double)n);
unsigned long x,y,z;
for(unsigned long i=2;i<=a;i++)
{
	for(int b=0; ; b++)
	{
		x= i*i; y= i*b;// Result of i^2,i^2+i,i^2+2i is serached in array with its index and replaced with 0 to denote that its not prime.
		z=x+y;
		if(z<n)
			arr[z]=0;
		else
			break;
	}
}

for(long i=m;i<n;i++)
{
	if(arr[i]!=0)
		std::cout<<"\n"<<arr[i];
}

delete [] arr;
}
int main()
{
	std::cout<<"Enter the value for no of testcases t (t<=10)\n";
	int t;
	std::cin>>t;
	if(t>10) { std::cout<<"\nNo more than 10 testcases please.\n"; return 1;}
	unsigned long m,n;
    for(int i=1;i<=t;i++)
{
	std::cout<<"Enter the range for testcase no "<< i << "\n";
	std::cin>>m;
	std::cin>>n;
	if (m<1 || n<1 || n < m || (n-m) >100000) { std::cout<<"\n Enter two numbers m and n such that 1<= m <= n <= 1000000000, n-m<=100000.\n"; return 1; }
	find_prime_fast(m,n);
	
	std::cout<<"\n";
}
   return 0;
}

Can you help?

[leppyr64]

Please use code tags when posting code.

Everything that you output is considered for the solution. The output for the sample input given in the problem statement is:

2
3
5
7
3
5

Your code outputs:

Enter the range 
1
2
3
5
7
Enter the range 
3

Also, it is not the solver's responsibility to enforce the constraints. The constraints are given for the solver's benefit and can safely be strictly followed. If the constraints are not correct there is usually many comments below the problem about the constraints being incorrect.

[ap00rva]

Hi,
I have edited the post to correct it. Now the c++ code is written in [code] tag.
Also the output messages are also show so that, user can enter right values.

[leppyr64]

The judge is not a user. It does not need to be prompted for input. The input is read and the output is generated and the judge compares the output to the expected result. This is the largest contributing factor to your WA. You also are outputting 1 as prime, but it is not prime.

[ap00rva]

Hey,
I haven't modified the code logic ,but I have removed the output messages. Still wrong answer

//2. Prime Generator
//Problem code: PRIME1
#include "iostream"
#include <stdio.h>
#include <math.h>
void find_prime_fast(unsigned long m, unsigned long n)
{
	unsigned long *arr = new(std::nothrow) unsigned long[n+1];
	if(arr==NULL)
	{	
		//std::cout<<"Memory could not be allocated";
		delete [] arr;
		return;
	}
    for (unsigned long i=0;i<n;i++)
{
	*(arr+i)=i;
}
unsigned long a=sqrt((long double)n);
unsigned long x,y,z;
for(unsigned long i=2;i<=a;i++)
{
	for(int b=0; ; b++)
	{
		x= i*i; y= i*b;// Result of i^2,i^2+i,i^2+2i is serached in array with its index and replaced with 0 to denote that its not prime.
		z=x+y;
		if(z<n)
			arr[z]=0;
		else
			break;
	}
}

for(long i=m;i<n;i++)
{
	if(arr[i]!=0 && arr[i]!=1)
		std::cout<<"\n"<<arr[i];
}

delete [] arr;
}
int main()
{
	//std::cout<<"Enter the value for no of testcases t (t<=10)\n";
	int t;
	std::cin>>t;
	if(t>10) { //std::cout<<"\nNo more than 10 testcases please.\n"; 
		return 1;}
	unsigned long m,n;
    for(int i=1;i<=t;i++)
{
	//std::cout<<"Enter the range for testcase no "<< i << "\n";
	std::cin>>m;
	std::cin>>n;
	if (m<1 || n<1 || n < m || (n-m) >100000) { //std::cout<<"\n Enter two numbers m and n such that 1<= m <= n <= 1000000000, n-m<=100000.\n"; 
		return 1; }
	find_prime_fast(m,n);
	
	std::cout<<"\n";
}
   return 0;
}

[leppyr64]

You can't make an array of size n. The fact that you are trapping the error means that you don't see the NZEC.