Trie Update

Trie Update

Author: careermonk

bin/chapter15stringalgorithms/Trie.class

@@ -0,0 +1,82 @@
+/*Copyright (c) Dec 22, 2014 CareerMonk Publications and others.
+ * E-Mail           	: info@careermonk.com 
+ * Creation Date    	: 2015-01-10 06:15:46 
+ * Last modification	: 2006-05-31 
+               by		: Narasimha Karumanchi 
+ * File Name			: Trie.java
+ * Book Title			: Data Structures And Algorithms Made In Java
+ * Warranty         	: This software is provided "as is" without any 
+ * 							warranty; without even the implied warranty of 
+ * 							merchantability or fitness for a particular purpose. 
+ * 
+ */
+
+
+package chapter15stringalgorithms;
+
+public class Trie {
+
+    private static final int ALPHABETS = 26;
+    private Trie[] links;
+    private boolean isEndOfString;
+
+    public Trie() {
+            links = new Trie[ALPHABETS];
+            isEndOfString = false;
+    }
+
+    public void addString(String s) {
+            Trie t = this;
+            int k;
+            int limit = s.length();
+            for (k = 0; k < limit; k++) {
+                    int index = s.charAt(k) - 'a';
+                    if (t.links[index] == null)
+                            t.links[index] = new Trie();
+                    t = t.links[index];
+            }
+            t.isEndOfString = true;
+    }
+
+    void print(String s, Trie t) {
+            if (t != null) {
+                    if (t.isEndOfString)
+                            System.out.println(s);
+                    int k;
+                    for (k = 0; k < ALPHABETS; k++)
+                            if (t.links[k] != null)
+                                    print(s + (char) (k + 'a'), t.links[k]);
+            }
+    }
+
+    public boolean isEndOfString(String s) {
+            Trie t = this;
+            int k;
+            int limit = s.length();
+            for (k = 0; k < limit; k++) {
+                    int index = s.charAt(k) - 'a';
+                    if (t.links[index] == null)
+                            return false;
+                    t = t.links[index];
+            }
+            return t.isEndOfString;
+    }
+
+    public boolean isEndOfString() {
+            return isEndOfString;
+    }
+
+    Trie childAt(char ch) {
+            return links[ch - 'a'];
+    }
+    
+    public static void main(String[] args) {
+            Trie t = new Trie();
+            t.addString("car"); t.addString("care"); t.addString("caree"); 
+            t.addString("career"); t.addString("careerm"); t.addString("careermonk");
+            System.out.println("Is careermo included? " + t.isEndOfString("careermo"));
+            System.out.println("Is career included? " + t.isEndOfString("career"));
+    }
+
+}
+

bin/chapter3linkedlists/RemoveDuplicatesBruteForce.class

@@ -15,7 +15,7 @@
 package chapter3linkedlists;
 
 public class RemoveDuplicatesBruteForce {
-	public static void removeDuplicates2(ListNode head) {
+	public static void removeDuplicates(ListNode head) {
 		ListNode curr = head;
 		if(curr == null || curr.getNext() == null) {
 			return; // 0 or 1 nodes in the list so no duplicates

bin/chapter3linkedlists/RemoveDuplicatesHashing.class

@@ -14,6 +14,24 @@
 
 package chapter3linkedlists;
 
-public class RemoveDuplicatesHashing {
+import java.util.HashMap;
+import java.util.Map;
 
+public class RemoveDuplicatesHashing {
+    // using a temporary buffer O(n)
+    public static void removeDuplicates(ListNode head) {
+        Map<Integer, Boolean> mapper = new HashMap<Integer, Boolean>();
+        ListNode curr = head;
+        ListNode next;
+        while (curr.getNext() != null) {
+            next = curr.getNext();
+            if(mapper.get(next.getData()) != null) {
+                // already seen it, so delete
+                curr.setNext(next.getNext());
+            } else {
+                mapper.put(next.getData(), true);
+                curr = curr.getNext();
+            }
+        }
+    }
 }