Merge pull request #283 from jeantimex/plus-one-linked-list

Plus One Linked List

Author: jeantimex

README.md

@@ -319,6 +319,7 @@ A collection of JavaScript problems and solutions for studying algorithms.
 
 - [Add Two Numbers](src/linked-list/add-two-numbers.js)
 - [Merge K Sorted Lists](src/linked-list/merge-k-sorted-lists.js)
+- [Plus One Linked List](src/linked-list/plus-one-linked-list.js)
 
 ### Dynamic Programming
 

src/linked-list/plus-one-linked-list.js

@@ -0,0 +1,60 @@
+/**
+ * Plus One Linked List
+ *
+ * Given a non-negative integer represented as non-empty a singly linked list of digits, plus one to the integer.
+ *
+ * You may assume the integer do not contain any leading zero, except the number 0 itself.
+ *
+ * The digits are stored such that the most significant digit is at the head of the list.
+ *
+ * Example:
+ *
+ * Input:
+ * 1->2->3
+ *
+ * Output:
+ * 1->2->4
+ */
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+const plusOne = head => {
+  if (dfs(head) === 0) {
+    return head;
+  }
+
+  const newHead = new ListNode(1);
+  newHead.next = head;
+  return newHead;
+};
+
+/**
+ * Returns the carry value
+ */
+const dfs = node => {
+  if (node === null) {
+    return 1;
+  }
+
+  const carry = dfs(node.next);
+
+  if (carry === 0) {
+    return 0;
+  }
+
+  const val = node.val + carry;
+  node.val = val % 10;
+  return Math.floor(val / 10);
+};
+
+export { plusOne };