update

Author: Blooverh

DataAndAlgoL/Chp3LinkedLists/Problem25_28.java

@@ -32,6 +32,6 @@ public static ListNode findMid(ListNode head){
             }
         }
 
-        return slow;
+        return slow; //return the slow pointer which points to the middle node
     }
 }

DataAndAlgoL/Chp3LinkedLists/Problem29.java

@@ -0,0 +1,21 @@
+package DataAndAlgoL.Chp3LinkedLists;
+
+/* Displaying a linked list from the end
+ * 
+ * Objective: recursively traverse until the end of the linked list, when coming back start printing the elements
+ */
+public class Problem29 {
+    public static void main(String[] args) {
+        
+    }   
+
+    public static void printListEnd(ListNode head){
+        if(head == null){
+            return;
+        }
+
+        printListEnd(head.getNext());
+        System.out.println(head.getData());
+    }
+
+}

DataAndAlgoL/Chp3LinkedLists/Problem2_5_6.java

@@ -3,7 +3,7 @@
 
 /*
  * Find the Nth Node from the end of a linked list 
- * Return that node once foud
+ * Return that node once found
  */
 public class Problem2_5_6 {
     public static void main(String[] args) {

DataAndAlgoL/Chp3LinkedLists/Problem30.java

@@ -0,0 +1,26 @@
+package DataAndAlgoL.Chp3LinkedLists;
+/*
+ * Check Whether the given linked list length is even or odd
+ * 
+ * OBJECTIVE : USE A POINTER THAT TRAVELS 2X (2 NODES AT A TIME)
+ * IF LENGTH IS EVEN POINTER WILL BE NULL, OTHER WISE IT IS NOT NULL
+ */
+public class Problem30 {
+    public static void main(String[] args) {
+        
+    }
+
+    public static int isEvenOrOddLength(ListNode head){
+        while(head != null && head.next != null){
+            head= head.next.next;
+        }
+
+        if(head == null){
+            return 0;
+        }
+
+        return 1;
+    }
+
+    
+}

DataAndAlgoL/Chp3LinkedLists/Problem32.java

@@ -0,0 +1,33 @@
+package DataAndAlgoL.Chp3LinkedLists;
+/*
+ * GIVEN 2 SORTED LIST L1 AND L2 WE NEED TO MERGE THEM INTO A NEW LIST IN SORTED ORDER
+ * 
+ */
+public class Problem32 {
+ 
+    public static void main(String[] args) {
+        
+    }
+
+    public static ListNode mergeTwoLists(ListNode head1, ListNode head2){
+        if(head1== null){
+            return head2;
+        }
+
+        if(head2 == null){
+            return head1;
+        }
+
+        ListNode head;
+
+        if(head1.getData() <= head2.getData()){
+            head=head1;
+            head.next=mergeTwoLists(head1.next, head2);
+        }else{
+            head=head2;
+            head.next=mergeTwoLists(head2.next, head1);
+        }
+
+        return head;
+    }
+}

DataAndAlgoL/Chp3LinkedLists/Problem34.java

@@ -0,0 +1,53 @@
+package DataAndAlgoL.Chp3LinkedLists;
+/*\
+ * Reverse the linked list in pairs. If you have a linked list that holds 
+ * 1→2→3→4→X, then after the function has been called the linked list would hold 2→1→4→3→X.
+ */
+public class Problem34 {
+    public static void main(String[] args) {
+        
+    }
+
+    //Recursive way
+    public static ListNode ReversePairsRec(ListNode head){
+        ListNode temp;
+        if(head== null || head.next== null){
+            return null; //base case for empty or 1 element list
+        }else{
+            //Reverse pair first
+            temp=head.next;
+            head.next=temp.next;
+            temp.next=head;
+            head=temp;
+            
+            //call method recursively for the rest of the list 
+            head.next.next=ReversePairsRec(head.next.next);
+            return head;
+            
+        }
+    }
+
+    //Iterative way
+    public static ListNode reversePairIte(ListNode head){
+        ListNode temp1=null;
+        ListNode temp2= null;
+
+        while(head != null && head.next != null){
+            if(temp1 != null){
+                temp1.next.next=head.next;
+            }
+
+            temp1= head.next;
+            head.next=head.next.next;
+            temp1.next= head;
+
+            if(temp2 ==null){
+                temp2=temp1;
+            }
+
+            head=head.next;
+        }
+
+        return temp2;
+    }
+}

DataAndAlgoL/Chp3LinkedLists/Problem38.java

@@ -0,0 +1,57 @@
+package DataAndAlgoL.Chp3LinkedLists;
+
+import java.util.List;
+
+/*
+ * Split a Circular Linked List into 2 equal parts if number of nodes is even
+ * if odd make first list one node extra than second List
+ */
+
+ /*ALGORITHM 
+  * > Store mid and last pointers of circular list using floyed cycle algorithm 
+    > Make second half circular 
+    >  Make first half circular
+    > set head pointers of the 2 linked lists
+  */
+public class Problem38 {
+    public static void main(String[] args) {
+        
+    }
+
+    public static void SplitList(ListNode head, ListNode head1, ListNode head2){
+        ListNode slow= head;
+        ListNode fast= head;
+
+        if(head== null){
+            return;
+        }
+
+        //If there are odd nodes in the circular list then fast.next becomes head 
+        //If its even nodes fast.next.next= head
+        while(fast.next != head && fast.next.next != head){
+            fast= fast.next.next;
+            slow= slow.next;
+        }
+
+        //If there are even elements in list the move fast pointer
+        if(fast.next.next != head){
+            fast=fast.next;
+        }
+
+        //set head pointer of 1st half
+        head1= head;
+
+        //set head pointer of second half
+        if(head.next != head){
+            head2=slow.next;
+        }
+
+        // make 2nd half circular 
+        fast.next= slow.next;
+
+        //make 1st half circular 
+        slow.next=head;
+    }
+
+
+}