68 lines
2.0 KiB
C++
68 lines
2.0 KiB
C++
#include "cQuicksort.h"
|
|
#include <ctype.h>
|
|
|
|
|
|
|
|
// Quicksort controller function, it partitions the different pieces of our array.
|
|
void cQuicksort::quicksort(int *arIntegers, int left, int right)
|
|
{
|
|
if (right > left)
|
|
{
|
|
int pivotIndex = median3(arIntegers,left,right);
|
|
int pivotNewIndex = partition(arIntegers, left, right, pivotIndex);
|
|
|
|
// Recursive call to quicksort to sort each half.
|
|
quicksort(arIntegers, left, pivotNewIndex-1);
|
|
quicksort(arIntegers, pivotNewIndex+1, right);
|
|
}
|
|
}
|
|
|
|
int cQuicksort::median3(int *arIntegers,int left,int right)
|
|
{
|
|
int center = (left+right)/2;
|
|
|
|
if(arIntegers[center] < arIntegers[left])
|
|
swap(arIntegers[left],arIntegers[center]);
|
|
if(arIntegers[right] < arIntegers[left])
|
|
swap(arIntegers[left],arIntegers[right]);
|
|
if(arIntegers[right] < arIntegers[center])
|
|
swap(arIntegers[center],arIntegers[right]);
|
|
|
|
swap(arIntegers[center],arIntegers[right-1]);
|
|
|
|
return center;
|
|
}
|
|
|
|
// This function takes an array (or one half an array) and sorts it.
|
|
// It then returns a new pivot index number back to quicksort.
|
|
int cQuicksort::partition(int *arIntegers, int left, int right, int pivot)
|
|
{
|
|
int pivotValue = arIntegers[pivot];
|
|
|
|
// Swap it out all the way to the end of the array
|
|
// So we know where it always is.
|
|
swap(arIntegers[pivot], arIntegers[right]);
|
|
int storeIndex = left;
|
|
|
|
// Move through the array from start to finish comparing each to our
|
|
// pivot value (not index, the value that was located at the pivot index)
|
|
for (int i = left; i < right; i++)
|
|
{
|
|
if (arIntegers[i] <= pivotValue)
|
|
{
|
|
swap(arIntegers[i], arIntegers[storeIndex]);
|
|
storeIndex++;
|
|
}
|
|
}
|
|
swap(arIntegers[storeIndex], arIntegers[right]);
|
|
return storeIndex;
|
|
}
|
|
|
|
// Simple swap function for our in place swapping.
|
|
void cQuicksort::swap(int &val1, int &val2)
|
|
{
|
|
int temp = val1;
|
|
val1 = val2;
|
|
val2 = temp;
|
|
}
|