sprime.cpp

USACO chapter one.May hope it useful to someone

/*
ID: chenkai4
PROG: sprime
LANG: C++
*/
#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
ifstream in("sprime.in");
ofstream out("sprime.out");

int N;

int nums[9]={0};

bool prime(int a)
{
	if(a==1||a==0) return false;int fuck=sqrt((double)a);
	for(int b=2;b<=fuck;b++)
		if(a%b==0)return false;
	return true;
}
int toint(int e)
{
	int b=1,answer=0;
	for(int a=1;a<=e-1;b*=10,a++);
	for(int a=1;a<=e;b/=10,a++)
		answer+=nums[a]*b;
	return answer;
}
void search(int n)
{
	if(n==N+1)
	{
		for(int a=1;a<=N;a++)
			out<<nums[a];
		out<<endl;
	}
	else
	{
		for(int a=0;a<=9;a++)
		{
			nums[n]=a;
			if(prime(toint(n)))
				search(n+1);
		}
	}
}

int main()
{
	in>>N;
	search(1);
	return 0;
}