Merge pull request #444 from santiago177/linked-list-extension

Modified the existing LinkedList code to add the printMiddle and getElement methods

Data Structures/LinkedLists/LinkedList.java

@@ -1,90 +1,126 @@
-// Java program to get intersection point of two linked list 
-
-class LinkedList { 
-
-    static Node head1, head2; 
-
-    static class Node { 
-
-        int data; 
-        Node next; 
-
-        Node(int d) { 
-            data = d; 
-            next = null; 
-        } 
-    } 
-
-    /*function to get the intersection point of two linked 
+// Java program to get intersection point of two linked list
+
+class LinkedList {
+
+    static Node head1, head2;
+
+    static class Node {
+
+        int data;
+        Node next;
+
+        Node(int d) {
+            data = d;
+            next = null;
+        }
+    }
+
+    public int getElement(Node node, int n) {
+    	//Function that returns the nth element of the given linked list
+    	Node current = node;
+    	int count = 0;
+    	int size = getCount(node);
+    	//Check if the given position is valid
+    	if(n >= size || n < 0) {
+    		System.out.println("Invalid position");
+    		return -1;
+    	}
+
+    	while(current != null && count < n) {
+    		count++;
+    		current = current.next;
+    	}
+    	return current.data;
+    }
+
+    public void printMiddle(Node list) {
+    	int size = getCount(list);
+    	 /*If the size of the list is even then print the two elements around the middle
+    	 otherwise just print a single element
+    	 if the list is empty don't do anything*/
+    	int middle = size/2;
+    	if(size % 2 == 0 && size > 0) {
+    		System.out.printf("%d %d\n", getElement(list, middle - 1), getElement(list, middle));
+    	}
+    	else if(size % 2 == 1) {
+    		System.out.printf("%d\n", getElement(list, middle));
+    	}
+    }
+
+    /*function to get the intersection point of two linked
     lists head1 and head2 */
-    int getNode() { 
-        int c1 = getCount(head1); 
-        int c2 = getCount(head2); 
-        int d; 
-  
-        if (c1 > c2) { 
-            d = c1 - c2; 
-            return _getIntesectionNode(d, head1, head2); 
-        } else { 
-            d = c2 - c1; 
-            return _getIntesectionNode(d, head2, head1); 
-        } 
-    } 
-  
-    /* function to get the intersection point of two linked 
-     lists head1 and head2 where head1 has d more nodes than 
+    int getNode() {
+        int c1 = getCount(head1);
+        int c2 = getCount(head2);
+        int d;
+
+        if (c1 > c2) {
+            d = c1 - c2;
+            return _getIntesectionNode(d, head1, head2);
+        } else {
+            d = c2 - c1;
+            return _getIntesectionNode(d, head2, head1);
+        }
+    }
+
+    /* function to get the intersection point of two linked
+     lists head1 and head2 where head1 has d more nodes than
      head2 */
-    int _getIntesectionNode(int d, Node node1, Node node2) { 
-        int i; 
-        Node current1 = node1; 
-        Node current2 = node2; 
-        for (i = 0; i < d; i++) { 
-            if (current1 == null) { 
-                return -1; 
-            } 
-            current1 = current1.next; 
-        } 
-        while (current1 != null && current2 != null) { 
-            if (current1.data == current2.data) { 
-                return current1.data; 
-            } 
-            current1 = current1.next; 
-            current2 = current2.next; 
-        } 
-  
-        return -1; 
-    } 
-  
-    /*Takes head pointer of the linked list and 
+    int _getIntesectionNode(int d, Node node1, Node node2) {
+        int i;
+        Node current1 = node1;
+        Node current2 = node2;
+        for (i = 0; i < d; i++) {
+            if (current1 == null) {
+                return -1;
+            }
+            current1 = current1.next;
+        }
+        while (current1 != null && current2 != null) {
+            if (current1.data == current2.data) {
+                return current1.data;
+            }
+            current1 = current1.next;
+            current2 = current2.next;
+        }
+
+        return -1;
+    }
+
+    /*Takes head pointer of the linked list and
     returns the count of nodes in the list */
-    int getCount(Node node) { 
-        Node current = node; 
-        int count = 0; 
-
-        while (current != null) { 
-            count++; 
-            current = current.next; 
-        } 
-
-        return count; 
-    } 
-
-    public static void main(String[] args) { 
-        LinkedList list = new LinkedList(); 
-
-        // creating first linked list 
-        list.head1 = new Node(3); 
-        list.head1.next = new Node(6); 
-        list.head1.next.next = new Node(15); 
-        list.head1.next.next.next = new Node(15); 
-        list.head1.next.next.next.next = new Node(30); 
-
-        // creating second linked list 
-        list.head2 = new Node(10); 
-        list.head2.next = new Node(15); 
-        list.head2.next.next = new Node(30); 
-
-        System.out.println("The node of intersection is " + list.getNode()); 
-
-    } 
+    int getCount(Node node) {
+        Node current = node;
+        int count = 0;
+
+        while (current != null) {
+            count++;
+            current = current.next;
+        }
+        return count;
+    }
+
+    public static void main(String[] args) {
+        LinkedList list = new LinkedList();
+
+        // creating first linked list
+        list.head1 = new Node(3);
+        list.head1.next = new Node(6);
+        list.head1.next.next = new Node(15);
+        list.head1.next.next.next = new Node(15);
+        list.head1.next.next.next.next = new Node(30);
+
+        // creating second linked list
+        list.head2 = new Node(10);
+        list.head2.next = new Node(15);
+        list.head2.next.next = new Node(30);
+
+        System.out.println("The node of intersection is " + list.getNode());
+
+        System.out.println(list.getElement(list.head1, 4));
+
+        System.out.println("Printing middle");
+        list.printMiddle(list.head2);
+        System.out.println(list.head1.data);
+    }
 }