infoarena

void prel(char *sir,int lu,unsigned long long k)
{
	int x;
	//sol-vectorul in care constr solutia
	//sir-sirul initial de carcatere
	//lu-lungimea sirului
	//initializari
	sol[0]=0;
	for (int i=1; i<=26; i++)
		next[i][lu+1]=0;
	for (int i=lu; i>0; i--)
	{
		x=sir[i]-'a'+1;
		next[x][i]=i;
		for (int j=1; j<x; j++)
			next[j][i]=next[j][i+1];
		for (int j=x+1; j<=26; j++)
			next[j][i]=next[j][i+1];
	}
	for (int i=lu; i>=1; i--)
	{
		din[i]=1;
		for (int j=1; j<=26; j++)
			din[i]+=din[next[j][i+1]];
	}
	//sfarsit initializari
	int p,e=1,q=1;
	//e-caracterul pe care incerc sa-l pun in solutie
	while (1)
	{
	p=next[e][q];  // p - poz de pe care incerc sa iau caracterul din sirul initial pt a-l pune in sol
	// q - pozitia (din sirul initial) imediat de dupa ultimul caracter pus in solutie
	while (din[p]<k)
	{
 		k=k-din[p];
	    e++;
		if ((e>26))
		{
			g<<-1<<endl;
			return;
		}
		p=next[e][q];
	}
	sol[0]++;//tin nr de caractere din solutie
	sol[sol[0]]='a'+e-1;
	e=1;
	k--;
	if (!k)
	{
		afis();//afiseaza solutia
		return;
	}
//	q=next[e][q];
   // q++;
	q=p+1;
	}
}

for (int i=lu; i>=1; i--)
	{
		din[i]=1;
		for (int j=1; j<=26; j++)
			if ((din[i]+din[next[j][i+1]])>(ULLONG_MAX))
				din[i]=ULLONG_MAX;
			else
				din[i]=din[i]+din[next[j][i+1]];
	}