Merge pull request #98 from jhanna60/main

Adding a heapsort algorithm

Author: jvm-coder

HeapSort.java

@@ -0,0 +1,91 @@
+import java.util.Scanner;
+
+public class HeapSort {
+    public static void heapify(int a[],int i,int n)
+    {
+
+        int l=2*i+1;
+        int r=2*i+2;
+
+
+        int temp,largest;
+
+        if(l<n && a[l]>a[i])
+            largest=l;
+        else
+            largest=i;
+
+        if(r<n && a[r]>a[largest])
+            largest=r;
+
+        if(largest !=i)
+        {
+            temp=a[largest];
+            a[largest]=a[i];
+            a[i]=temp;
+
+            heapify(a,largest,n);
+        }
+
+
+    }
+
+    public static void bheap(int a[])
+    {
+
+        for(int i=(a.length/2)-1;i>=0;i--)
+        {
+
+            heapify(a,i,a.length);
+
+        }
+
+    }
+
+    public static void Sort(int a[])
+    {
+        int temp,j,i;
+
+        bheap(a);
+
+        for( i=(a.length)-1; i>0;)
+        {
+            temp=a[0];
+            a[0]=a[i];
+            a[i]=temp;
+            heapify(a,0,i--) ;
+
+        }
+
+    }
+
+    public static void printarray(int a[])
+    {
+        System.out.println();
+        for (int j : a) {
+
+            System.out.print(j + " ");
+        }
+
+    }
+    public static void main(String[] args)
+    {
+        int n, res,i;
+        Scanner s = new Scanner(System.in);
+        System.out.print("Enter number of elements in the array:");
+        n = s.nextInt();
+        int[] a = new int[n];
+        System.out.println("Enter "+n+" elements ");
+        for( i=0; i < n; i++)
+        {
+            a[i] = s.nextInt();
+        }
+
+        System.out.println( "elements in array ");
+        printarray(a);
+        Sort(a);
+        System.out.println( "\nelements after sorting");
+        printarray(a);
+
+    }
+}