Algorithms/kminheap.cpp at master · mandy1628/Algorithms · GitHub

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#include<bits/stdc++.h>

using namespace std;

void restoreDown(int arr[], int len, int index,
										int k)
{

	int child[k+1];

	while (1)
	{

		for (int i=1; i<=k; i++)
			child[i] = ((k*index + i) < len) ?
					(k*index + i) : -1;

		int max_child = -1, max_child_index ;

		for (int i=1; i<=k; i++)
		{
			if (child[i] != -1 &&
				arr[child[i]] > max_child)
			{
				max_child_index = child[i];
				max_child = arr[child[i]];
			}
		}


		if (max_child == -1)
			break;


		if (arr[index] < arr[max_child_index])
			swap(arr[index], arr[max_child_index]);

		index = max_child_index;
	}
}


void restoreUp(int arr[], int index, int k)
{


	int parent = (index-1)/k;


	while (parent>=0)
	{
		if (arr[index] > arr[parent])
		{
			swap(arr[index], arr[parent]);
			index = parent;
			parent = (index -1)/k;
		}


		else
			break;
	}
}


void buildHeap(int arr[], int n, int k)
{


	for (int i= (n-1)/k; i>=0; i--)
		restoreDown(arr, n, i, k);
}


void insert(int arr[], int* n, int k, int elem)
{

	arr[*n] = elem;


	*n = *n+1;


	restoreUp(arr, *n-1, k);
}


int extractMax(int arr[], int* n, int k)
{

	int max = arr[0];


	arr[0] = arr[*n-1];


	*n = *n-1;


	restoreDown(arr, *n, 0, k);

	return max;
}


int main()
{
	const int capacity = 100;
	int arr[capacity] = {4, 5, 6, 7, 8, 9, 10};
	int n = 7;
	int k = 3;

	buildHeap(arr, n, k);

	printf("Built Heap : \n");
	for (int i=0; i<n; i++)
		printf("%d ", arr[i]);

	int element = 3;
	insert(arr, &n, k, element);

	printf("\n\nHeap after insertion of %d: \n",
			element);
	for (int i=0; i<n; i++)
		printf("%d ", arr[i]);

	printf("\n\nExtracted max is %d",
				extractMax(arr, &n, k));

	printf("\n\nHeap after extract max: \n");
	for (int i=0; i<n; i++)
		printf("%d ", arr[i]);

	return 0;
}