Added example for adding two integers

Author: anitaa

src/linkedlist/AddTwoIntegers.java

@@ -0,0 +1,136 @@
+package linkedlist;
+
+public class AddTwoIntegers {
+
+
+    /*
+     * Given head pointers of two linked lists where each linked list represents an integer number
+     * (each node is a digit), add them and return the resulting linked list.
+     * Input: List1: 1,2,3  List: 1,2
+     * Output: 2, 4, 3
+     *
+     * Runtime Complexity:
+     * Linear, O(n)
+     *
+     * Memory Complexity:
+     * Constant, O(1)
+     *
+     * Add the integers 9901 and 237. The result of this addition would be 10138.
+     * */
+
+    static LinkedList.Node addIntegers(LinkedList.Node integer1,
+                                       LinkedList.Node integer2) {
+
+        LinkedList.Node result = null;
+        LinkedList.Node last = null;
+        int carry = 0;
+
+        while (
+                integer1 != null ||
+                        integer2 != null ||
+                        carry > 0) {
+
+            int first = (integer1 == null ? 0 : integer1.data);
+            int second = (integer2 == null ? 0 : integer2.data);
+            int sum = first + second + carry;
+            LinkedList.Node pNew = new LinkedList.Node(sum % 10);
+            carry = sum / 10;
+            if (result == null) {
+                result = pNew;
+            } else {
+                last.next = pNew;
+            }
+
+            last = pNew;
+            if (integer1 != null) {
+                integer1 = integer1.next;
+            }
+            if (integer2 != null) {
+                integer2 = integer2.next;
+            }
+        }
+        return result;
+    }
+
+    protected static class LinkedList {
+
+        private Node head;
+
+        public Node head() {
+            return head;
+        }
+
+        public void printNode(Node node) {
+            while (node != null) {
+                System.out.print(node.data + " ");
+                node = node.next;
+            }
+        }
+
+        /* Inserts a new Node at end of the list. */
+        public void push(int new_data) {
+            Node newNode = new Node(new_data);
+            if (head == null) {
+                head = new Node(new_data);
+                return;
+            }
+
+            newNode.next = null;
+            Node last = head;
+            while (last.next != null) {
+                last = last.next;
+            }
+            last.next = newNode;
+        }
+
+        public static class Node {
+            private Node next;
+            private Integer data;
+
+            public Node(Integer data) {
+                this.data = data;
+            }
+
+            public Node next() {
+                return next;
+            }
+
+            public void setNext(Node next) {
+                this.next = next;
+            }
+
+            public Integer data() {
+                return data;
+            }
+
+            public void setData(Integer data) {
+                this.data = data;
+            }
+        }
+    }
+
+
+    public static void main(String[] args) {
+
+        LinkedList linkedList1 = new LinkedList();
+        linkedList1.push(1);
+        linkedList1.push(2);
+        linkedList1.push(3);
+
+
+        LinkedList linkedList2 = new LinkedList();
+        linkedList2.push(1);
+        linkedList2.push(2);
+
+        System.out.println("List 1: ");
+        linkedList1.printNode(linkedList1.head);
+        System.out.println();
+
+        System.out.println("List 2: ");
+        linkedList2.printNode(linkedList2.head);
+        System.out.println();
+
+        LinkedList.Node mergedList = addIntegers(linkedList1.head, linkedList2.head);
+        linkedList1.printNode(mergedList);
+    }
+}