Advanced Sorting - Advanced Topics in Java: Core Concepts in Data Structures - page 259

We can now write heapSort as follows:
public static void heapSort(int[] num, int n) {
//sort num[1] to num[n]
//convert the array to a heap
for (int k = n / 2; k >= 1; k--) siftDown(num[k], num, k, n);
for (int k = n; k > 1; k--) {
int item = num[k]; //extract current last item
num[k] = num[1]; //move top of heap to current last node
siftDown(item, num, 1, k-1); //restore heap properties from 1 to k-1
}
} //end heapSort
We can test heapSort with Program P9.1.
Program P9.1
import java.io.*;
public class HeapSortTest {
public static void main(String[] args) throws IOException {
int[] num = {0, 37, 25, 43, 65, 48, 84, 73, 18, 79, 56, 69, 32};
int n = 12;
heapSort(num, n);
for (int h = 1; h <= n; h++) System.out.printf("%d ", num[h]);
System.out.printf("\n");
}
public static void heapSort(int[] num, int n) {
//sort num[1] to num[n]
//convert the array to a heap
for (int k = n / 2; k >= 1; k--) siftDown(num[k], num, k, n);
for (int k = n; k > 1; k--) {
int item = num[k]; //extract current last item
num[k] = num[1]; //move top of heap to current last node
siftDown(item, num, 1, k-1); //restore heap properties from 1 to k-1
}
} //end heapSort
public static void siftDown(int key, int[] num, int root, int last) {
int bigger = 2 * root;
while (bigger <= last) { //while there is at least one child
if (bigger < last) //there is a right child as well; find the bigger
if (num[bigger+1] > num[bigger]) bigger++;
//'bigger' holds the index of the bigger child
if (key >= num[bigger]) break;
//key is smaller; promote num[bigger]
num[root] = num[bigger];
root = bigger;
bigger = 2 * root;
}