Added minheap test-file

minheap.cpp

@@ -0,0 +1,184 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+#include <stdexcept>
+using namespace std;
+
+// Data structure for Min Heap
+struct PriorityQueue 
+{
+private:
+	// vector to store heap elements
+	vector<int> A;
+
+	// return parent of A[i]
+	// don't call this function if i is already a root node
+	int PARENT(int i) 
+	{ 
+		return (i - 1) / 2; 
+	}
+
+	// return left child of A[i]	
+	int LEFT(int i) 
+	{ 
+		return (2 * i + 1); 
+	}
+
+	// return right child of A[i]	
+	int RIGHT(int i) 
+	{ 
+		return (2 * i + 2); 
+	}
+
+	// Recursive Heapify-down algorithm
+	// the node at index i and its two direct children
+	// violates the heap property
+	void heapify_down(int i)
+	{
+		// get left and right child of node at index i
+		int left = LEFT(i);
+		int right = RIGHT(i);
+
+		int smallest = i;
+
+		// compare A[i] with its left and right child
+		// and find smallest value
+		if (left < size() && A[left] < A[i])
+			smallest = left;
+
+		if (right < size() && A[right] < A[smallest])
+			smallest = right;
+
+		// swap with child having lesser value and 
+		// call heapify-down on the child
+		if (smallest != i) {
+			swap(A[i], A[smallest]);
+			heapify_down(smallest);
+		}
+	}
+
+	// Recursive Heapify-up algorithm
+	void heapify_up(int i)
+	{
+		// check if node at index i and its parent violates 
+		// the heap property
+		if (i && A[PARENT(i)] > A[i]) 
+		{
+			// swap the two if heap property is violated
+			swap(A[i], A[PARENT(i)]);
+
+			// call Heapify-up on the parent
+			heapify_up(PARENT(i));
+		}
+	}
+
+public:
+	// return size of the heap
+	unsigned int size()
+	{
+		return A.size();
+	}
+
+	// function to check if heap is empty or not
+	bool empty()
+	{
+		return size() == 0;
+	}
+
+	// insert key into the heap
+	void push(int key)
+	{
+		// insert the new element to the end of the vector
+		A.push_back(key);
+
+		// get element index and call heapify-up procedure
+		int index = size() - 1;
+		heapify_up(index);
+	}
+
+	// function to remove element with lowest priority (present at root)
+	void pop()
+	{
+		try {
+			// if heap has no elements, throw an exception
+			if (size() == 0)
+				throw out_of_range("Vector<X>::at() : "
+						"index is out of range(Heap underflow)");
+
+			// replace the root of the heap with the last element
+			// of the vector
+			A[0] = A.back();
+			A.pop_back();
+
+			// call heapify-down on root node
+			heapify_down(0);
+		}
+		// catch and print the exception
+		catch (const out_of_range& oor) {
+			cout << "\n" << oor.what();
+		}
+	}
+
+	// function to return element with lowest priority (present at root)
+	int top()
+	{
+		try {
+			// if heap has no elements, throw an exception
+			if (size() == 0)
+				throw out_of_range("Vector<X>::at() : "
+						"index is out of range(Heap underflow)");
+
+			// else return the top (first) element
+			return A.at(0);	// or return A[0];
+		}
+		// catch and print the exception
+		catch (const out_of_range& oor) {
+			cout << "\n" << oor.what();
+		}
+	}
+};
+
+// Min Heap C++ Implementation
+int main()
+{
+	PriorityQueue pq;
+
+	// Note - Priority is decided by element's value
+
+	pq.push(3);
+	pq.push(2);
+	pq.push(15);
+
+	cout << "Size is " << pq.size() << endl;	
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	pq.push(5);
+	pq.push(4);
+	pq.push(45);
+
+	cout << endl << "Size is " << pq.size() << endl;
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	cout << pq.top() << " ";
+	pq.pop();
+
+	cout << endl << std::boolalpha << pq.empty();
+
+	pq.top();	// top operation on an empty heap
+	pq.pop();	// pop operation on an empty heap
+
+	return 0;
+}