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min_heap method for kth smallest element in java

Tense Tapir answered on January 5, 2022 Popularity 8/10 Helpfulness 4/10

answer min_heap method for kth smallest element in java

min_heap method for kth smallest element in java

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// A Java program to find k'th smallest element using min heap
import java.util.*;
class GFG
{
  
  // A class for Max 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
  
    int parent(int i) { return (i - 1) / 2; }
    int left(int i) { return ((2 * i )+ 1); }
    int right(int i) { return ((2 * i) + 2); }
    int getMin() { return harr[0]; } // Returns minimum
  
    // to replace root with new node x and heapify() new root
    void replaceMax(int x)
    {
      this.harr[0] = x;
      minHeapify(0);
    }
    MinHeap(int a[], int size)
    {
      heap_size = size;
      harr = a; // store address of array
      int i = (heap_size - 1) / 2;
      while (i >= 0)
      {
        minHeapify(i);
        i--;
      }
    }
  
    // Method to remove maximum element (or root) from min heap
    int extractMin()
    {
      if (heap_size == 0)
        return Integer.MAX_VALUE;
  
      // Store the maximum vakue.
      int root = harr[0];
  
      // If there are more than 1 items, move the last item to root
      // and call heapify.
      if (heap_size > 1)
      {
        harr[0] = harr[heap_size - 1];
        minHeapify(0);
      }
      heap_size--;
      return root;
    }
  
    // A recursive method to heapify a subtree with root at given index
    // This method assumes that the subtrees are already heapified
    void 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) 
      {
        int t = harr[i];
        harr[i] = harr[smallest];
        harr[smallest] = t;
        minHeapify(smallest);
      }
    }
  };
  
  // Function to return k'th largest element in a given array
  int kthSmallest(int arr[], int n, int k)
  {
  
    // Build a heap of first k elements: O(k) time
    MinHeap mh = new MinHeap(arr, n);
  
    // Process remaining n-k elements. If current element is
    // smaller than root, replace root with current element
    for (int i = 0; i < k - 1; i++)
      mh.extractMin();
  
    // Return root
    return mh.getMin();
  }
  
  // Driver program to test above methods
  public static void main(String[] args)
  {
    int arr[] = { 12, 3, 5, 7, 19 };
    int n = arr.length, k = 2;
    GFG gfg = new GFG();
    System.out.print("K'th smallest element is " + 
                     gfg.kthSmallest(arr, n, k));
  }
}
  
// This code is contributed by avanitrachhadiya2155

Popularity 8/10 Helpfulness 4/10 Language whatever

Source: www.geeksforgeeks.org

Tags: element java whatever

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Contributed on Jan 05 2022

Tense Tapir

0 Answers Avg Quality 2/10

min_heap method for kth smallest element in java

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