✨ [q2] js

Author: enkr1

2_add_two_numbers/solution.js

@@ -0,0 +1,85 @@
+function ListNode(val, next) {
+  this.val = (val === undefined ? 0 : val)
+  this.next = (next === undefined ? null : next)
+}
+
+/**
+ * @param {ListNode} l1
+ * @param {ListNode} l2
+ * @return {ListNode}
+ */
+// Input: l1 = [2,4,3], l2 = [5,6,4]
+// Output: [7,0,8]
+// Explanation: 342 + 465 = 807.
+
+var addTwoNumbers = function (l1, l2) {
+  let num_carried = 0
+  let res, curr = null;
+
+  while (l1 || l2) {
+    let num1, num2, val = 0;
+
+    if (l1) {
+      num1 = l1.val;
+      l1 = l1.next;
+    }
+    if (l2) {
+      num2 = l2.val;
+      l2 = l2.next;
+    }
+
+    val = num1 + num2 + num_carried;
+
+    if (val > 9) { // 10, 11, 12, etc.
+      val = val - 10;
+      num_carried = 1;
+    } else {
+      num_carried = 0;
+    }
+
+    // QUESTION: I dont understand this ifelse and how is res being set.
+    if (res) {
+      console.log(`--- have ${val} ---`)
+      console.log("res:")
+      console.log(res)
+      console.log("curr:")
+      console.log(curr)
+      // console.log("curr.next:")
+      // console.log(curr.next)
+
+      curr.next = new ListNode(val);
+      curr = curr.next;
+
+      console.log("res:")
+      console.log(res)
+      console.log("curr:")
+      console.log(curr)
+
+    } else {
+      console.log("dont have aka first time")
+      res = new ListNode(val);
+      curr = res;
+    }
+
+    // if (res) {
+    //   curr.next = new ListNode(val);
+    //   curr = curr.next;
+    // } else {
+    //   res = new ListNode(val);
+    //   curr = res;
+    // }
+
+  }
+
+  if (num_carried) curr.next = new ListNode(num_carried);
+
+  // QUESTION: How is res being set???
+  return res;
+}
+
+
+// addTwoNumbers([2, 4, 3], [5, 6, 4])
+addTwoNumbers(
+  ListNode(2, ListNode(4, ListNode(3))),
+  ListNode(5, ListNode(6, ListNode(4)))
+)