HeapSort.java

public class HeapSort 
{ 
    public void sort(int arr[]) 
    { 
        int n = arr.length; 
  
        
        for (int i = n / 2 - 1; i >= 0; i--) 
            heapify(arr, n, i); 
  
        
        for (int i=n-1; i>0; i--) 
        { 
             
            int temp = arr[0]; 
            arr[0] = arr[i]; 
            arr[i] = temp; 
  
            
            heapify(arr, i, 0); 
        } 
    } 
  
    
    void heapify(int arr[], int n, int i) 
    { 
        int largest = i; // Initialize largest as root 
        int l = 2*i + 1; // left = 2*i + 1 
        int r = 2*i + 2; // right = 2*i + 2 
  
        
        if (l < n && arr[l] > arr[largest]) 
            largest = l; 
  
       
        if (r < n && arr[r] > arr[largest]) 
            largest = r; 
  
        
        if (largest != i) 
        { 
            int swap = arr[i]; 
            arr[i] = arr[largest]; 
            arr[largest] = swap; 
  
            
            heapify(arr, n, largest); 
        } 
    } 
  
    /* A utility function to print array of size n */
    static void printArray(int arr[]) 
    { 
        int n = arr.length; 
        for (int i=0; i<n; ++i) 
            System.out.print(arr[i]+" "); 
        System.out.println(); 
    } 
  
    // Driver program 
    public static void main(String args[]) 
    { 
        int arr[] = {12, 11, 13, 5, 6, 7}; 
        int n = arr.length; 
  
        HeapSort ob = new HeapSort(); 
        ob.sort(arr); 
  
        System.out.println("Sorted array is"); 
        printArray(arr); 
    } 
}