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Cod sursa(job #800591)
/*
* Randomized Quicksort which switches to selection sort
* when the size of the subarray is small enough.
* Also in the partitioning step we use two pivots and partition
* the array into three: smaller, equal and larger.
*/
#include <fstream>
#include <cstdlib>
using namespace std;
ifstream fin("algsort.in");
ofstream fout("algsort.out");
int sw = 15;
int v[500001], n;
void quicksort(int l, int r)
{
if(r - l > sw)
{
/* finding the pivot element and partitionig around it */
int i, q, j, aux;
i = l + rand() % (r-l+1); // pick a random pivot
aux = v[i]; v[i] = v[r]; v[r] = aux;
for(i = l-1, q = l-1, j = l; j <= r-1; j++)
if(v[j] <= v[r])
{
aux = v[++i];
v[i] = v[j];
v[j] = aux;
if(v[i] < v[r])
{
q++;
if(q != i)
{
aux = v[q];
v[q] = v[i];
v[i] = aux;
}
}
}
aux = v[++i];
v[i] = v[r];
v[r] = aux;
/* finished partitioning */
quicksort(l, q);
quicksort(i+1, r);
}
else if(l < r)
{
int i, j, aux;
for(i = l+1; i <= r; ++i)
for(j = i-1; j >= l && v[j] > v[j+1]; --j)
{
aux = v[j]; v[j] = v[j+1]; v[j+1] = aux;
}
}
}
int main()
{
int i;
srand(16);
fin >> n;
for(i = 1; i <= n; ++i)
fin >> v[i];
quicksort(1, n);
for(i = 1; i <= n; ++i)
fout << v[i] << ' ';
fout << endl;
fin.close();
fout.close();
return 0;
}