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Cod sursa(job #369660)
#include <fstream>
using namespace std;
#define MAX_N 3000005
ifstream fin ("sdo.in");
ofstream fout ("sdo.out");
int A[MAX_N], N, K;
void citire()
{
fin >> N >> K;
for(int i = 1; i <= N; ++i)
fin >> A[i];
}
int part(int A[MAX_N], int li, int lf)
{
int i = li-1, j = lf+1, p = A[li + (rand()%(lf-li+1))];
while(1)
{
do
{
++i;
} while(A[i] < p);
do
{
--j;
} while(p < A[j]);
if(i < j)
swap(A[i], A[j]);
else
return j;
}
return 0;
}
void sel(int A[MAX_N], int li, int lf, int k)
{
if(li == lf)
return;
int q = part(A, li, lf);
int t = q-li+1;
if(t >= k)
sel(A, li, q, k);
else
sel(A, q+1, lf, k-t);
}
int main()
{
citire();
sel(A, 1, N, K);
fout << A[K] << "\n";
}