Create Heap,java

Java_Programs-master/Heap,java

@@ -0,0 +1,96 @@
+import java.util.*;
+
+
+class Heap{
+
+	int heapSize;
+
+	void build_max_heap(int[] a)
+	{
+		heapSize=a.length;
+		for(int i=(heapSize/2);i>=0;i--)
+			max_heapify(a,i);
+
+	}
+
+	void max_heapify(int[] a,int i)
+	{
+		int l=2*i+1;
+		int r=2*i+2;
+		int largest=i;
+		if(l<heapSize &&a[l]>a[largest])
+			largest=l;
+		if(r<heapSize &&a[r]>a[largest])
+			largest=r;
+		if(largest!=i)
+		{
+			int t=a[i];
+			a[i]=a[largest];
+			a[largest]=t;
+		    max_heapify(a,largest);
+		}
+
+	}
+
+	//to delete the max element
+
+	int extract_max(int[] a)
+	{
+		if(heapSize<0)
+			System.out.println("underflow");
+		int max=a[0];
+		a[0]=a[heapSize-1];
+		heapSize--;
+		max_heapify(a,0);
+		return max;
+	}
+
+	void increase_key(int[] a,int i,int key)
+	{
+		if(key<a[i])
+			System.out.println("error");
+		a[i]=key;
+		while(i>=0 && a[(i-1)/2]<a[i])
+		{
+			int t=a[(i-1)/2];
+			a[(i-1)/2]=a[i];
+			a[i]=t;
+
+			i=(i-1)/2;
+		}
+	}
+
+	void print_heap(int a[])
+	{
+		for(int i=0;i<heapSize;i++)
+		    System.out.println(a[i]+" ");
+	}
+}
+
+public class HeapDemo{
+
+	public static void main(String[] args)
+	{
+		Scanner in=new Scanner(System.in);
+		int n=in.nextInt();
+		int a[]=new int[n];
+
+		System.out.println("enter the elements of array");
+
+		for(int i=0;i<n;i++)
+		  a[i]=in.nextInt();
+	         Heap ob=new Heap();
+
+		ob.build_max_heap(a);
+		ob.print_heap(a);
+
+
+		System.out.println("maximum element is : "+ob.extract_max(a));
+		ob.print_heap(a);
+		System.out.println("maximum element is : "+ob.extract_max(a));
+		ob.increase_key(a,6,800);
+		ob.print_heap(a);
+
+	}
+
+}