From dd4264d9a92108af7b23b07b47670ef5eec72432 Mon Sep 17 00:00:00 2001
From: garud-dwar <115369078+garud-dwar@users.noreply.github.com>
Date: Sat, 8 Oct 2022 23:37:32 +0530
Subject: [PATCH] Create heap implementation

---
 heap implementation | 159 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 159 insertions(+)
 create mode 100644 heap implementation

diff --git a/heap implementation b/heap implementation
new file mode 100644
index 0000000..9112c19
--- /dev/null
+++ b/heap implementation	
@@ -0,0 +1,159 @@
+// A C++ program to demonstrate common Binary Heap Operations
+#include<iostream>
+#include<climits>
+using namespace std;
+
+// Prototype of a utility function to swap two integers
+void swap(int *x, int *y);
+
+// A class for Min Heap
+class MinHeap
+{
+	int *harr; // pointer to array of elements in heap
+	int capacity; // maximum possible size of min heap
+	int heap_size; // Current number of elements in min heap
+public:
+	// Constructor
+	MinHeap(int capacity);
+
+	// to heapify a subtree with the root at given index
+	void MinHeapify(int );
+
+	int parent(int i) { return (i-1)/2; }
+
+	// to get index of left child of node at index i
+	int left(int i) { return (2*i + 1); }
+
+	// to get index of right child of node at index i
+	int right(int i) { return (2*i + 2); }
+
+	// to extract the root which is the minimum element
+	int extractMin();
+
+	// Decreases key value of key at index i to new_val
+	void decreaseKey(int i, int new_val);
+
+	// Returns the minimum key (key at root) from min heap
+	int getMin() { return harr[0]; }
+
+	// Deletes a key stored at index i
+	void deleteKey(int i);
+
+	// Inserts a new key 'k'
+	void insertKey(int k);
+};
+
+// Constructor: Builds a heap from a given array a[] of given size
+MinHeap::MinHeap(int cap)
+{
+	heap_size = 0;
+	capacity = cap;
+	harr = new int[cap];
+}
+
+// Inserts a new key 'k'
+void MinHeap::insertKey(int k)
+{
+	if (heap_size == capacity)
+	{
+		cout << "\nOverflow: Could not insertKey\n";
+		return;
+	}
+
+	// First insert the new key at the end
+	heap_size++;
+	int i = heap_size - 1;
+	harr[i] = k;
+
+	// Fix the min heap property if it is violated
+	while (i != 0 && harr[parent(i)] > harr[i])
+	{
+	swap(&harr[i], &harr[parent(i)]);
+	i = parent(i);
+	}
+}
+
+// Decreases value of key at index 'i' to new_val. It is assumed that
+// new_val is smaller than harr[i].
+void MinHeap::decreaseKey(int i, int new_val)
+{
+	harr[i] = new_val;
+	while (i != 0 && harr[parent(i)] > harr[i])
+	{
+	swap(&harr[i], &harr[parent(i)]);
+	i = parent(i);
+	}
+}
+
+// Method to remove minimum element (or root) from min heap
+int MinHeap::extractMin()
+{
+	if (heap_size <= 0)
+		return INT_MAX;
+	if (heap_size == 1)
+	{
+		heap_size--;
+		return harr[0];
+	}
+
+	// Store the minimum value, and remove it from heap
+	int root = harr[0];
+	harr[0] = harr[heap_size-1];
+	heap_size--;
+	MinHeapify(0);
+
+	return root;
+}
+
+
+// This function deletes key at index i. It first reduced value to minus
+// infinite, then calls extractMin()
+void MinHeap::deleteKey(int i)
+{
+	decreaseKey(i, INT_MIN);
+	extractMin();
+}
+
+// A recursive method to heapify a subtree with the root at given index
+// This method assumes that the subtrees are already heapified
+void MinHeap::MinHeapify(int i)
+{
+	int l = left(i);
+	int r = right(i);
+	int smallest = i;
+	if (l < heap_size && harr[l] < harr[i])
+		smallest = l;
+	if (r < heap_size && harr[r] < harr[smallest])
+		smallest = r;
+	if (smallest != i)
+	{
+		swap(&harr[i], &harr[smallest]);
+		MinHeapify(smallest);
+	}
+}
+
+// A utility function to swap two elements
+void swap(int *x, int *y)
+{
+	int temp = *x;
+	*x = *y;
+	*y = temp;
+}
+
+// Driver program to test above functions
+int main()
+{
+	MinHeap h(11);
+	h.insertKey(3);
+	h.insertKey(2);
+	h.deleteKey(1);
+	h.insertKey(15);
+	h.insertKey(5);
+	h.insertKey(4);
+	h.insertKey(45);
+	cout << h.extractMin() << " ";
+	cout << h.getMin() << " ";
+	h.decreaseKey(2, 1);
+	cout << h.getMin();
+	return 0;
+}