add two no.s represented by lists: done

Author: Ram swaroop

src/me/ramswaroop/linkedlists/AddNumbersInTwoLists.java

@@ -0,0 +1,79 @@
+package me.ramswaroop.linkedlists;
+
+import me.ramswaroop.common.SingleLinkedList;
+import me.ramswaroop.common.SingleLinkedNode;
+
+/**
+ * Created by IntelliJ IDEA.
+ *
+ * @author: ramswaroop
+ * @date: 7/2/15
+ * @time: 1:20 PM
+ */
+public class AddNumbersInTwoLists {
+
+    /**
+     * Adds two numbers represented by two linked lists {@param list1}
+     * and {@param list2} and stores them in another list.
+     * <p/>
+     * Example:
+     * <p/>
+     * Input:
+     * First List: 5->6->3              // represents number 365
+     * Second List: 8->4->2             //  represents number 248
+     * Output:
+     * Resultant list: 3->1->6          // represents number 613
+     * <p/>
+     * Input:
+     * First List: 7->5->9->4->6        // represents number 64957
+     * Second List: 8->4                //  represents number 48
+     * Output:
+     * Resultant list: 5->0->0->5->6    // represents number 65005
+     *
+     * @param list1
+     * @param list2
+     * @return list containing the sum of numbers in {@param list1} and {@param list2}.
+     */
+    public static SingleLinkedList<Integer> add(SingleLinkedList<Integer> list1,
+                                                SingleLinkedList<Integer> list2) {
+
+        int sum, carry = 0;
+        SingleLinkedNode<Integer> curr1 = list1.head, curr2 = list2.head;
+        SingleLinkedList<Integer> resultList = new SingleLinkedList<>();
+
+        // loop till both of the list runs out
+        while (curr1 != null || curr2 != null) {
+
+            // if either of the list runs out first
+            int a = (curr1 != null) ? curr1.item : 0;
+            int b = (curr2 != null) ? curr2.item : 0;
+
+            sum = (a + b + carry) % 10;
+            carry = (a + b + carry) / 10;
+            resultList.add(sum);
+
+            if (curr1 != null) curr1 = curr1.next;
+            if (curr2 != null) curr2 = curr2.next;
+        }
+
+        // if there is any carry left over, add it to the result
+        if (carry != 0) resultList.addFirst(carry);
+
+        return resultList;
+    }
+
+    public static void main(String a[]) {
+        SingleLinkedList<Integer> linkedList1 = new SingleLinkedList<>();
+        linkedList1.add(7);
+        linkedList1.add(5);
+        linkedList1.add(9);
+        linkedList1.add(4);
+        linkedList1.add(6);
+        linkedList1.printList();
+        SingleLinkedList<Integer> linkedList2 = new SingleLinkedList<>();
+        linkedList2.add(8);
+        linkedList2.add(4);
+        linkedList2.printList();
+        add(linkedList1, linkedList2).printList();
+    }
+}