Pagini recente » Cod sursa (job #2140712) | Cod sursa (job #960493) | Cod sursa (job #345768) | Cod sursa (job #2704995) | Cod sursa (job #800592)
Cod sursa(job #800592)
/*
* Randomized Quicksort which switches to selection sort
* when the size of the subarray is smaller than sw.
* Also we use 3-way partitioning i.e. in the partitioning
* step we use two pivots and partition the array into
* three: strictly smaller, equal and strictly larger.
*/
#include <fstream>
#include <cstdlib>
using namespace std;
ifstream fin("algsort.in");
ofstream fout("algsort.out");
int sw = 16; /* the value at which the algorithm switches to selection sort */
int v[500001], n;
void quicksort(int l, int r)
{
int i, j, q, aux;
if(r - l > sw) /* if the size of the subarray is larger than sw we use quicksort */
{
/* pick a random element from the subarray */
i = l + rand() % (r-l+1);
/* set the random element to be the pivot */
aux = v[i]; v[i] = v[r]; v[r] = aux;
/* do the 3-way partitioning */
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) != i)
aux = v[q], v[q] = v[i], v[i] = aux;
}
/* put the pivot in its correct place in the subbarray */
aux = v[++i]; v[i] = v[r]; v[r] = aux;
/* finished partitioning */
quicksort(l, q);
quicksort(i+1, r);
}
else if(l < r) /* if the size of the subarray is smaller than sw we use insertion sort */
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); /* seed value for the RNG */
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;
}