2.5 solution

Author: amejiarosario

linked-list/sum-lists.js

@@ -1,6 +1,14 @@
 const LinkedList = require('./linkedlist');
 
-function sumLists(list1, list2, isForwardOrder = false) {
+function sumLists(list1, list2, {isForwardOrder} = {isForwardOrder: false}) {
+  if(isForwardOrder) {
+    return sumListsForwardOrder(list1, list2);
+  } else {
+    return sumListsReverseOrder(list1, list2);
+  }
+}
+
+function sumListsReverseOrder(list1, list2) {
   const result = new LinkedList();
   let reminder = 0;
 
@@ -15,22 +23,62 @@ function sumLists(list1, list2, isForwardOrder = false) {
   return result;
 }
 
-function test() {
+function sumListsForwardOrder(list1, list2) {
+  const result = new LinkedList();
+  let values = [];
+  let num = 0;
+
+  // TODO: assert list length are the same
+
+  for(let l1 = list1.head, l2 = list2.head; l1 && l2; l1 = l1.next, l2 = l2.next) {
+    // TODO: validate data from both list are numbers
+    values.push(l1.data + l2.data);
+  }
+
+  for(let i = 0; i < values.length; i++) {
+    num += values[i] * Math.pow(10, values.length - i - 1);
+  }
+
+  num.toString().split('').reduce((list, e) => { list.addLast(e); return list; }, result);
+
+  return result;
+}
+
+function test1() {
+  const list1 = new LinkedList();
+  list1.addFirst(6);
+  list1.addFirst(1);
+  list1.addFirst(7);
+
+
+  const list2 = new LinkedList();
+  list2.addFirst(2);
+  list2.addFirst(9);
+  list2.addFirst(5);
+
+
+  console.log(list1.toString()); // 7 -> 1 -> 6
+  console.log(list2.toString()); // 5 -> 9 -> 2
+  console.log(sumLists(list1, list2).toString()); // 2 -> 1 -> 9 = 912
+}
+
+function test2() {
   const list1 = new LinkedList();
-  list1.add(6);
-  list1.add(1);
-  list1.add(7);
+  list1.addLast(6);
+  list1.addLast(1);
+  list1.addLast(7);
 
 
   const list2 = new LinkedList();
-  list2.add(2);
-  list2.add(9);
-  list2.add(5);
+  list2.addLast(2);
+  list2.addLast(9);
+  list2.addLast(5);
 
 
-  console.log(list1.toString());
-  console.log(list2.toString());
-  console.log(sumLists(list1, list2).toString());
+  console.log(list1.toString()); // 6 -> 1 -> 7
+  console.log(list2.toString()); // 2 -> 9 -> 5
+  console.log(sumLists(list1, list2, {isForwardOrder: true}).toString()); // 9 -> 1 -> 2 = 912
 }
 
-test();
+// test1();
+test2();