Question

// CMPS 390 // MinHeap.java // Complete 4 methods: getMin, add, removeMin, reheap public class MinHeap { private Comparable a heap; // array of heap entries private static final int DEFAULT MAX SIZE = 100; private int lastIndex; // index of last entry public MinHeap() { heap = new Comparable (DEFAULT_MAX_SIZE]; lastIndex = 0; } // end default constructor public MinHeap (int maxSize) { heap = new Comparable (maxSize); lastIndex = 0; } // end constructor public MinHeap (Comparable[] entries) { lastIndex = entries.length; heap = new Comparable (lastIndex + 1]; // copy given array to data field for (int index = 0; index < entries.length; index++) heap (index+1] = entries (index]; // create heap for (int index = heap.length/2; index > 0; index--) reheap (index); } // end constructor public Comparable getMin() { Comparable root = null; // ADD YOUR CODE HERE return root; ) // end getMin public boolean isEmpty() { return lastIndex < 1; } // end is Empty public int getSize() { return lastIndex; } // end getSize public void clear() { for (i lastIndex > -1; lastIndex--) heap [last Index] = null; last Index = 0; ) // end clear public void add (Comparable newEntry) { // ADD YOUR CODE HERE } // end add public Comparable removeMin() { Comparable root = null; // ADD YOUR CODE HERE return root; } // end removeMin private void reheap (int root Index) { // ADD YOUR CODE HERE } // end reheap public void display() { int size = getSize(); System.out.println("\nThe Min Heap has " + size + "items"); for (int i = 1; i <= size; i++) System.out.print (heap[i] + " "); System.out.println(); } // end display 1 // end MinHeap

Answer 1

You are using comparable class which is not declared and adding String values into heap. So, for better understanding I am using String array instead of comparable array, if you have comparable class then change the declarations from String to comparable. Since we are using String at the place of null I am returning empty string("")

public void add(String newEntry){

if(lastIndex==heap.length-1){

System.out.println("Heap is already full");

return;

}

//Add the element at the end of the heap

heap[++lastIndex]=newEntry;
int current=lastIndex;

//Check whether it's parent element is greater or not If yes then run the loop until the condition is false.
while(current>1 && heap[current].compareTo(heap[current/2])<0){

String temp=heap[current];
heap[current]=heap[current/2];
heap[current/2]=temp;
current=current/2;

}

}

public String getMin(){

//Min element will be the starting element of the heap

String root="";
if(isEmpty()) return root;
root=heap[1];
return root;

}

public String removeMin(){

String root="";
if(isEmpty()) return root;
root=heap[1];

//replace the 1st element with the last element and use reheap(1) as we changed 1st element
heap[1]=heap[lastIndex];
heap[lastIndex]="";
--lastIndex;
reheap(1);
return root;

}

public void reheap(int index){

//check whether the index is the leaf element or not

if(!(index >= (lastIndex / 2) && index <= lastIndex)){

int left=2*index;
int right=2*index+1;

//Compare the parent element with leftchild and right child
if(heap[index].compareTo(heap[left])>0 || heap[index].compareTo(heap[right])>0){

//If left child is the smallest among 3 then swap(left child, parent elements) and recursively call for the left child element

if(heap[left].compareTo(heap[right])<0){

String temp=heap[index];
heap[index]=heap[left];
heap[left]=temp;
reheap(2*index);

}

//Similarly to the right child element

else{

String temp=heap[index];
heap[index]=heap[right];
heap[right]=temp;
reheap(2*index+1);

}

}

}

}