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897_precalculo.cpp
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897_precalculo.cpp
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#include <cstdio>
#include <iostream>
#include <string>
#include <bitset>
#include <vector>
#include <algorithm>
#include <iterator>
#define MAX 10000000 //raiz de 10 000 000=3162.xx +1
#define LIM 8 //total de 10^algo
using namespace std;
bitset <MAX> criba;
vector <int> primos;
vector <int> cosa;
int lim[LIM]={1,10,100,1000,10000,100000,1000000,10000000};
int maxval[LIM]={2,11,101,1009,10007,100003,1000003,9999991};
void llena_criba() {
criba.set();
criba.reset(0);
criba.reset(1);
for (int i=2;i<MAX;i++)
if (criba.test(i)){
primos.push_back(i);
for(int j=2*i;j<MAX;j+=i)
criba.reset(j);
}
}
int main(){
#ifndef ONLINE_JUDGE
freopen("897.in","r",stdin);
#endif
char tmp[20];
string cad;
int i,n;
vector <int>::iterator it;
llena_criba();
for (i=0;i<primos.size();i++){
if (criba[primos[i]]){
sprintf(tmp,"%d",primos[i]);
cad=tmp;
sort(cad.begin(),cad.end());
//cout<<"r"<<endl;
do {
//el numero -> cadena permutada-> numero
n=atoi(cad.c_str());
//cout<<n<<" "<<criba[n]<<endl;
if (!criba[n]){
n=-1;//no
break;
}
}while(next_permutation(cad.begin(),cad.end()));
//cout<<"p"<<endl;
//n es usada como bandera -1 no
if (n==-1){
criba[primos[i]]=0;
}else
cosa.push_back(primos[i]);
}
}
cout<<"numeros precalculados"<<endl;
for (i=0;i<cosa.size();i++){
cout<<cosa[i]<<endl;
}
return 0;
while(scanf("%d",&n)==1 && n!=0){
for (i=0;i<LIM;i++){
if (lim[i]>n)
break;
}
//el rango de cosas a buscar es de n+1 a 10^i
n++;
//busco al cosa-primo mas cercano (por la izq) a n
it=lower_bound(cosa.begin(), cosa.end(), n);
//barre hasta encontrar un primo permutable
if(*it<maxval[i] && *it>=n){
printf("%d\n",*it);
}else
printf("0\n",n);
}
return 0;
}