add lesson8 homework

lesson4/src/RelatedList.java

@@ -21,6 +21,7 @@ public boolean equals(Object o) {
     }
 
     private Node<T> head;
+    private Node<T> nextItem;
 
     public RelatedList() {
         head = null;
@@ -36,6 +37,17 @@ public void insert(T c) {
         head = n;
     }
 
+    public T find(T t) {
+        Node<T> n = new Node<>(t);
+        Node<T> current = head;
+        while (!current.equals(n)) {
+            if (current.next == null)
+                return null;
+            current = current.next;
+        }
+        return current.c;
+    }
+
     public T remove() {
         if (isEmpty())
             return null;
@@ -55,7 +67,26 @@ public boolean contains(T c) {
         }
         return true;
     }
-
+
+    public T delete(T t) {
+        Node<T> current = head;
+        Node<T> previous = head;
+        while (!current.c.equals(t)) {
+            if (current.next == null)
+                return null;
+            else {
+                previous = current;
+                current = current.next;
+            }
+        }
+        if (current == head)
+            head = head.next;
+        else
+            previous.next = current.next;
+
+        return current.c;
+    }
+
     public T delete(String name) {
         Node<T> current = head;
         Node<T> previous = head;
@@ -87,4 +118,21 @@ public String toString() {
         }
         return sb.toString();
     }
+
+    public boolean hasNext() {
+        if (head == null)
+            return false;
+        if (nextItem == null)
+            return true;
+        return nextItem.next != null;
+    }
+
+    public T next () {
+        if (nextItem == null) {
+            nextItem = head;
+            return nextItem.c;
+        }
+        nextItem = nextItem.next;
+        return nextItem.c;
+    }
 }

lesson8/src/HashTable.java

@@ -1,19 +1,21 @@
 public class HashTable {
     private Item[] hashArr;
+    private RelatedList<Item>[] chainedHashTable;
     private int arrSize;
     private Item nullItem;
 
     public HashTable(int arrSize) {
         this.arrSize = arrSize;
         hashArr = new Item[arrSize];
         nullItem = new Item(-1);
+        chainedHashTable = new RelatedList[arrSize];
     }
 
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
         for (int i = 0; i < arrSize; i++) {
-            sb.append((hashArr[i] != null) ? hashArr[i].getKey() : "*");
+            sb.append((chainedHashTable[i] != null) ? chainedHashTable[i] : "*");
             if (i < arrSize - 1) {
                 sb.append(", ");
             }
@@ -25,6 +27,14 @@ private int hashFunc(int key) {
         return key % arrSize;
     }
 
+    public void chainedInsert(Item item) {
+        int key = item.getKey();
+        int hash = hashFunc(key);
+        if (chainedHashTable[hash] == null)
+            chainedHashTable[hash] = new RelatedList<>();
+        chainedHashTable[hash].insert(item);
+    }
+
     public void insert(Item item) {
         int key = item.getKey();
         int hashVal = hashFunc(key);
@@ -43,6 +53,16 @@ public void insert(Item item) {
         hashArr[hashVal] = item;
     }
 
+    public Item chainedFind(int key) {
+        int hash = hashFunc(key);
+        while (chainedHashTable[hash].hasNext()) {
+            Item item = chainedHashTable[hash].next();
+            if (item.getKey() == key)
+                return item;
+        }
+        return null;
+    }
+
     public Item find(int key) {
         int hashVal = hashFunc(key);
 //        int step = 0;
@@ -64,6 +84,16 @@ int dblHashFunc(int key) {
         return  19 - (key % 19);
     }
 
+    public Item chainedDelete(int key) {
+        int hash = hashFunc(key);
+        while (chainedHashTable[hash].hasNext()) {
+            Item item = chainedHashTable[hash].next();
+            if (item.getKey() == key)
+                return chainedHashTable[hash].delete(item);
+        }
+        return  null;
+    }
+
     public Item delete(int key) {
         int hashVal = hashFunc(key);
 //        int step = 0;

lesson8/src/Item.java

@@ -23,4 +23,9 @@ public boolean equals(Object o) {
     public int hashCode() {
         return Objects.hash(data);
     }
+
+    @Override
+    public String toString() {
+        return Integer.toString(data);
+    }
 }

lesson8/src/Online.java

@@ -2,12 +2,12 @@ public class Online {
     public static void main(String[] args) {
         HashTable ht = new HashTable(25);
         for (int i = 0; i < 11; i++) {
-            ht.insert(new Item(i * 5));
+            ht.chainedInsert(new Item(i * 5));
         }
         System.out.println(ht);
-        ht.delete(25);
+        ht.chainedDelete(25);
         System.out.println(ht);
-        ht.insert(new Item(75));
+        ht.chainedInsert(new Item(75));
         System.out.println(ht);
     }
 }