Questions Needed...!!

[rat genius797]

hi guys...nice to meet ya all..!! anyway...hey guys i need some questions on c++ to enable my self to emphasize my skills..!! hope u guys can make question so tat i can practice much...!!thanks...i can do till function..!! anyway im kinda newbie 2yrs in c++

[cppjsan]

Hi this is cppjsan, and i'm trying to get the first 100 emirps. i've written this much code but now i'm stuck an d confused. geratful for your help.

#include <iostream>
#include <fstream>

using namespace std;
void reverse ();
bool isPrime;

int main()
{
	// variables
	int rev_numb;
	int digit_1;
	int digit_10;
	int digit_100;
	int digit_1000;
	int numb;
	//	bool isPrime ();
	for (int numb=1; numb<=10; numb++)
	{
		// check if prime
		isPrime=true;
		if (numb%2 == 0)
		{
			isPrime=false;
		}
		else
		{
			for (int i=3; i<=numb/2; i=i+2)
			{
				if (numb%i == 0)
				{
					isPrime=false;
					break;
				}
			}
		}

		// print if number is prime
		if (isPrime)
		{
			reverse ();
			cout << numb << "\t";
		}
	}
	// save the number
	//bool isPrime=numb;

	// strip out the digits
	digit_1=numb % 10;
	numb=numb / 10;
	digit_10=numb % 10;
	numb=numb / 10;
	digit_100=numb %10;
	numb=numb / 10;
	digit_1000=numb;

	// reverse the number
	rev_numb=(digit_1*1000)+(digit_10*100)+(digit_100*10)
		+(digit_1000);

	// print out the reversed number
	cout << "the number reversed = " << rev_numb << "\n\n";

	// test to see if it is a palidrome
	if (numb == rev_numb)
	{
		cout << "It is a palidrome.";
	}

	return 0;
}

[cppjsan]

Hi this is cppjsan, and i'm trying to get the first 100 emirps. i've written this much code but now i'm stuck an d confused. geratful for your help.

#include <iostream>
#include <fstream>

using namespace std;
void reverse ();
bool isPrime;

int main()
{
	// variables
	int rev_numb;
	int digit_1;
	int digit_10;
	int digit_100;
	int digit_1000;
	int numb;
	//	bool isPrime ();
	for (int numb=1; numb<=10; numb++)
	{
		// check if prime
		isPrime=true;
		if (numb%2 == 0)
		{
			isPrime=false;
		}
		else
		{
			for (int i=3; i<=numb/2; i=i+2)
			{
				if (numb%i == 0)
				{
					isPrime=false;
					break;
				}
			}
		}

		// print if number is prime
		if (isPrime)
		{
			reverse ();
			cout << numb << "\t";
		}
	}
	// save the number
	//bool isPrime=numb;

	// strip out the digits
	digit_1=numb % 10;
	numb=numb / 10;
	digit_10=numb % 10;
	numb=numb / 10;
	digit_100=numb %10;
	numb=numb / 10;
	digit_1000=numb;

	// reverse the number
	rev_numb=(digit_1*1000)+(digit_10*100)+(digit_100*10)
		+(digit_1000);

	// print out the reversed number
	cout << "the number reversed = " << rev_numb << "\n\n";

	// test to see if it is a palidrome
	if (numb == rev_numb)
	{
		cout << "It is a palidrome.";
	}

	return 0;
}

[yang]

#include "stdafx.h"
#include <iostream>
#include <math.h>
#include <vector>

using namespace std;

//reverse a num and return
int reverse_num(vector <int>::iterator Iter, int digits);

int _tmain(int argc, _TCHAR* argv[])
{
	double n;
	cout<<"Type in the scope of your prime table:";
	cin>>n;

	//use vector to save primes
	vector <int> prime;
	vector <int>::iterator prime_Iter;
	bool isprime;
	//take 2 as first prime(someone use 3)
	prime.push_back(2);
	for (int i = 3; i < n; i++)
	{
		isprime = true;
		for ( prime_Iter = prime.begin( ) ; prime_Iter != prime.end() && *prime_Iter < sqrt(n) + 1; prime_Iter++ )
		{
			if (i % *prime_Iter == 0)
				isprime = false; 
		}
		if (isprime == true)
		{
			prime.push_back(i);
		}
	}

	//////////////////////////////////////////////////////////////////////////
	
	cout << "prime =" ;
	for ( prime_Iter = prime.begin( ) ; prime_Iter != prime.end( ) ; prime_Iter++ )
		cout << " " << *prime_Iter;
	cout << endl;
	
	//////////////////////////////////////////////////////////////////////////
	cout << "emirps =";
	
	//mark the length of a prime
	//do nothing for primes under 10
	int digits = 10;
	
	//the reversed number
	int rev = 0;

	//start flag
	//search prime from the first num with the same digits
	bool startflag = true;
	vector <int>::iterator start = prime.begin();

	for ( prime_Iter = prime.begin( ) ; prime_Iter != prime.end( ); prime_Iter++ )
	{
		if (*prime_Iter / digits < 1)
		{
			//do nothing
		}
		else if ( *prime_Iter / digits < 10)
		{
			//get the reverse_num;
			rev = reverse_num(prime_Iter,digits);

			//mark a start point
			if (startflag)
			{
				start = prime_Iter;
				startflag = false;
			}
			
			//find if the reverse_num is also a prime
			for(vector <int>::iterator point = start; point != prime.end() && *point / digits < 10;point++) 
			{
				if (*point == rev)
				{
					cout << *prime_Iter << " ";
					break;
				}
				else
				{
					continue;
				}
			}
		}
		else if(10 <= *prime_Iter / digits)
		{
			digits *=10;
			startflag = true;
		}
	}
	cout << endl;
	return 0;
}

int reverse_num(vector <int>::iterator Iter, int digits)
{
	int temp = *Iter;
	int sum = 0;
	while (digits>=1)
	{
		sum*=10;
		sum += temp%10;
		temp/=10;
		digits/=10;
	}
	return sum;
};

[rat genius797]

anyway wads bool prime?? wads the function of it??