create heap.cpp

heap.cpp

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+// 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; 
+}