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Diffstat (limited to 'converter/cQuicksort.cpp')
-rw-r--r-- | converter/cQuicksort.cpp | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/converter/cQuicksort.cpp b/converter/cQuicksort.cpp new file mode 100644 index 000000000..8a00805eb --- /dev/null +++ b/converter/cQuicksort.cpp @@ -0,0 +1,67 @@ +#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; +} |