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| import java.util.*;
class Program {
public static int[] heapSort(int[] array) {
buildMaxHeap(array);
int endIdx = array.length - 1;
while (endIdx > 0) {
siftDown(array, 0, endIdx);
swap(array, 0, endIdx);
endIdx -= 1;
}
return array;
}
public static int[] buildMaxHeap(int[] array) {
if (array.length == 0)
return array;
int firstParentIdx = (array.length - 2) / 2;
for (int i = firstParentIdx; i >= 0; i--) {
siftDown(array, i, array.length - 1);
}
return array;
}
public static void siftDown(int[] array, int currentIdx, int endIdx) {
int leftChildIdx = currentIdx * 2 + 1;
while (leftChildIdx <= endIdx) {
int rightChildIdx = leftChildIdx + 1;
int idxToSwap = leftChildIdx;
if (rightChildIdx <= endIdx && array[rightChildIdx] > array[leftChildIdx]) {
idxToSwap = rightChildIdx;
}
if (array[idxToSwap] > array[currentIdx]) {
swap(array, idxToSwap, currentIdx);
currentIdx = idxToSwap;
leftChildIdx = currentIdx * 2 + 1;
} else {
return;
}
}
}
public static void swap(int[] array, int idx1, int idx2) {
int tmp = array[idx1];
array[idx1] = array[idx2];
array[idx2] = tmp;
}
}
|
