Merge pull request #1325 from mariaRoxana94/fix-error

Fixed 8XCorrectness_Bugs + 10XBad_Practice_Bugs + 14XDodgy_Code_Bugs

DataStructures/DynamicArray/DynamicArray.java

@@ -41,7 +41,7 @@ public class DynamicArray<E> implements Iterable<E> {
     }
 
     public void put(final int index, E element) {
-        Objects.checkIndex(index, this.size);
+//        Objects.checkIndex(index, this.size);
 
         this.elements[index] = element;
     }
@@ -79,7 +79,7 @@ public class DynamicArray<E> implements Iterable<E> {
     }
 
     private E getElement(final int index) {
-        Objects.checkIndex(index, this.size);
+//        Objects.checkIndex(index, this.size);
         return (E) this.elements[index];
     }
 

DataStructures/Graphs/BellmanFord.java

@@ -23,7 +23,7 @@ start vertex, end vertes and weights. Vertices should be labelled with a number
         * @param v End vertex
         * @param c Weight
         */
-        Edge(int a,int b,int c)
+        public Edge(int a,int b,int c)
         {
             u=a;
             v=b;

DataStructures/Graphs/MatrixGraphs.java

@@ -127,8 +127,7 @@ class AdjacencyMatrixGraph {
      * @return returns a string describing this graph
      */
     public String toString() {
-        String s = new String();
-        s = "    ";
+        String s = "    ";
         for (int i = 0; i < this.numberOfVertices(); i++) {
             s = s + String.valueOf(i) + " ";
         }

DataStructures/Heaps/HeapElement.java

@@ -117,7 +117,21 @@ public class HeapElement {
      * @return true if the keys on both elements are identical and the additional info objects
      * are identical.
      */
-    public boolean equals(HeapElement otherHeapElement) {
-        return (this.key == otherHeapElement.key) && (this.additionalInfo.equals(otherHeapElement.additionalInfo));
+    @Override
+    public boolean equals(Object o) {
+        if (o != null) {
+            if (!(o instanceof HeapElement)) return false;
+            HeapElement otherHeapElement = (HeapElement) o;
+            return (this.key == otherHeapElement.key) && (this.additionalInfo.equals(otherHeapElement.additionalInfo));
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = 0;
+        result = 31*result + (int) key;
+        result = 31*result + (additionalInfo != null ? additionalInfo.hashCode() : 0);
+        return result;
     }
 }

DataStructures/Heaps/MaxHeap.java

@@ -49,9 +49,9 @@ public class MaxHeap implements Heap {
     // Toggle an element up to its right place as long as its key is lower than its parent's
     private void toggleUp(int elementIndex) {
         double key = maxHeap.get(elementIndex - 1).getKey();
-        while (getElementKey((int) Math.floor(elementIndex / 2)) < key) {
-            swap(elementIndex, (int) Math.floor(elementIndex / 2));
-            elementIndex = (int) Math.floor(elementIndex / 2);
+        while (getElementKey((int) Math.floor(elementIndex / 2.0)) < key) {
+            swap(elementIndex, (int) Math.floor(elementIndex / 2.0));
+            elementIndex = (int) Math.floor(elementIndex / 2.0);
         }
     }
 
@@ -101,7 +101,7 @@ public class MaxHeap implements Heap {
         maxHeap.set(elementIndex - 1, getElement(maxHeap.size()));
         maxHeap.remove(maxHeap.size());
         // Shall the new element be moved up...
-        if (getElementKey(elementIndex) > getElementKey((int) Math.floor(elementIndex / 2))) toggleUp(elementIndex);
+        if (getElementKey(elementIndex) > getElementKey((int) Math.floor(elementIndex / 2.0))) toggleUp(elementIndex);
             // ... or down ?
         else if (((2 * elementIndex <= maxHeap.size()) && (getElementKey(elementIndex) < getElementKey(elementIndex * 2))) ||
                 ((2 * elementIndex < maxHeap.size()) && (getElementKey(elementIndex) < getElementKey(elementIndex * 2))))

DataStructures/Heaps/MinHeap.java

@@ -44,9 +44,9 @@ public class MinHeap implements Heap {
     // Toggle an element up to its right place as long as its key is lower than its parent's
     private void toggleUp(int elementIndex) {
         double key = minHeap.get(elementIndex - 1).getKey();
-        while (getElementKey((int) Math.floor(elementIndex / 2)) > key) {
-            swap(elementIndex, (int) Math.floor(elementIndex / 2));
-            elementIndex = (int) Math.floor(elementIndex / 2);
+        while (getElementKey((int) Math.floor(elementIndex / 2.0)) > key) {
+            swap(elementIndex, (int) Math.floor(elementIndex / 2.0));
+            elementIndex = (int) Math.floor(elementIndex / 2.0);
         }
     }
 
@@ -96,7 +96,7 @@ public class MinHeap implements Heap {
         minHeap.set(elementIndex - 1, getElement(minHeap.size()));
         minHeap.remove(minHeap.size());
         // Shall the new element be moved up...
-        if (getElementKey(elementIndex) < getElementKey((int) Math.floor(elementIndex / 2))) toggleUp(elementIndex);
+        if (getElementKey(elementIndex) < getElementKey((int)Math.floor(elementIndex / 2.0))) toggleUp(elementIndex);
             // ... or down ?
         else if (((2 * elementIndex <= minHeap.size()) && (getElementKey(elementIndex) > getElementKey(elementIndex * 2))) ||
                 ((2 * elementIndex < minHeap.size()) && (getElementKey(elementIndex) > getElementKey(elementIndex * 2))))

DataStructures/Lists/CircleLinkedList.java

@@ -14,7 +14,7 @@ public class CircleLinkedList<E> {
     //For better O.O design this should be private allows for better black box design
     private int size;
     //this will point to dummy node;
-    private Node<E> head;
+    private Node<E> head =  null;
 
     //constructer for class.. here we will make a dummy node for circly linked list implementation with reduced error catching as our list will never be empty;
     public CircleLinkedList() {

DataStructures/Lists/DoublyLinkedList.java

@@ -86,9 +86,12 @@ public class DoublyLinkedList {
     public Link deleteHead() {
         Link temp = head;
         head = head.next; // oldHead <--> 2ndElement(head)
-        head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
-        if (head == null)
+
+        if (head == null) {
             tail = null;
+        } else {
+            head.previous = null; // oldHead --> 2ndElement(head) nothing pointing at old head so will be removed
+        }
         return temp;
     }
 
@@ -100,10 +103,13 @@ public class DoublyLinkedList {
     public Link deleteTail() {
         Link temp = tail;
         tail = tail.previous; // 2ndLast(tail) <--> oldTail --> null
-        tail.next = null; // 2ndLast(tail) --> null
+
         if (tail == null) {
             head = null;
+        } else{
+            tail.next = null; // 2ndLast(tail) --> null
         }
+
         return temp;
     }
 

DataStructures/Stacks/NodeStack.java

@@ -74,7 +74,7 @@ public class NodeStack<Item> {
         } else {
         	newNs.setPrevious(NodeStack.head);
         	NodeStack.head.setNext(newNs);
-        	NodeStack.head = newNs;
+        	NodeStack.head.setHead(newNs);
         }
 
         NodeStack.setSize(NodeStack.getSize() + 1);
@@ -89,7 +89,7 @@ public class NodeStack<Item> {
 
     	Item item = (Item) NodeStack.head.getData();
 
-    	NodeStack.head = NodeStack.head.getPrevious();
+        NodeStack.head.setHead(NodeStack.head.getPrevious());
     	NodeStack.head.setNext(null);
 
     	NodeStack.setSize(NodeStack.getSize() - 1);

DataStructures/Trees/LevelOrderTraversal.java

@@ -15,8 +15,8 @@ public class LevelOrderTraversal {
     // Root of the Binary Tree
     Node root;
 
-    public LevelOrderTraversal() {
-        root = null;
+    public LevelOrderTraversal( Node root) {
+        this.root = root;
     }
 
     /* function to print level order traversal of tree*/

DataStructures/Trees/LevelOrderTraversalQueue.java

@@ -19,11 +19,9 @@ public class LevelOrderTraversalQueue {
         }
     }
 
-    Node root;
-
     /* Given a binary tree. Print its nodes in level order
      using array for implementing queue  */
-    void printLevelOrder() {
+    void printLevelOrder(Node root) {
         Queue<Node> queue = new LinkedList<Node>();
         queue.add(root);
         while (!queue.isEmpty()) {

DataStructures/Trees/ValidBSTOrNot.java

@@ -13,14 +13,13 @@ public class ValidBSTOrNot {
     }
 
     //Root of the Binary Tree
-    Node root;
  
     /* can give min and max value according to your code or
     can write a function to find min and max value of tree. */
 
     /* returns true if given search tree is binary
      search tree (efficient version) */
-    boolean isBST() {
+    boolean isBST(Node root) {
         return isBSTUtil(root, Integer.MIN_VALUE,
                 Integer.MAX_VALUE);
     }