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Java Heap Sort
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Java Heap Sort
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import java.util.*;
public class HeapSortMain {
public static void buildheap(int []arr) {
/*
* As last non leaf node will be at (arr.length-1)/2
* so we will start from this location for heapifying the elements
* */
for(int i=(arr.length-1)/2; i>=0; i--){
heapify(arr,i,arr.length-1);
}
}
public static void heapify(int[] arr, int i,int size) {
int left = 2*i+1;
int right = 2*i+2;
int max;
if(left <= size && arr[left] > arr[i]){
max=left;
} else {
max=i;
}
if(right <= size && arr[right] > arr[max]) {
max=right;
}
// If max is not current node, exchange it with max of left and right child
if(max!=i) {
exchange(arr,i, max);
heapify(arr, max,size);
}
}
public static void exchange(int[] arr,int i, int j) {
int t = arr[i];
arr[i] = arr[j];
arr[j] = t;
}
public static int[] heapSort(int[] arr) {
buildheap(arr);
int sizeOfHeap=arr.length-1;
for(int i=sizeOfHeap; i>0; i--) {
exchange(arr,0, i);
sizeOfHeap=sizeOfHeap-1;
heapify(arr, 0,sizeOfHeap);
}
return arr;
}
public static void main(String[] args) {
int[] arr={1,10,16,19,3,5};
System.out.println("Before Heap Sort : ");
System.out.println(Arrays.toString(arr));
arr=heapSort(arr);
System.out.println("=====================");
System.out.println("After Heap Sort : ");
System.out.println(Arrays.toString(arr));
}
}