/*
* Copyright (C) 2015-2019 Mateusz Łącki and Michał Startek.
*
* This file is part of IsoSpec.
*
* IsoSpec is free software: you can redistribute it and/or modify
* it under the terms of the Simplified ("2-clause") BSD licence.
*
* IsoSpec is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* You should have received a copy of the Simplified BSD Licence
* along with IsoSpec. If not, see <https://opensource.org/licenses/BSD-2-Clause>.
*/
#include "misc.h"
#include "platform.h"
#include <stdlib.h>
#define mswap(x, y) swapspace = x; x = y; y=swapspace;
namespace IsoSpec
{
void* quickselect(void** array, int n, int start, int end)
{
void* swapspace;
if(start == end)
return array[start];
while(true)
{
// Partition part
int len = end - start;
#if ISOSPEC_BUILDING_R
int pivot = len/2 + start;
#else
int pivot = rand() % len + start;
#endif
void* pval = array[pivot];
double pprob = getLProb(pval);
mswap(array[pivot], array[end-1]);
int loweridx = start;
for(int i=start; i<end-1; i++)
{
if(getLProb(array[i]) < pprob)
{
mswap(array[i], array[loweridx]);
loweridx++;
}
}
mswap(array[end-1], array[loweridx]);
// Selection part
if(n==loweridx)
return array[n];
if(n<loweridx)
end = loweridx;
else
start = loweridx+1;
};
}
} // namespace IsoSpec