369. Plus One Linked List

/**

* Lock by Leetcode

* 369. Plus One Linked List

* https://www.lintcode.com/problem/plus-one-linked-list/description

*

* 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

Given head = 1 -> 2 -> 3 -> null, return 1 -> 2 -> 4 -> null.

*/

* @param head: the first Node

* @return: the answer after plus one

const plusOne = function (head) {

　　let str = "";

　　while (head != null) {

　　　　str += head.val;

　　　　head = head.next;

　　}

　　let resultStr = addTwoString(str, "1");

　　let arr = resultStr.split("");

　　let newHead = new ListNode(parseInt(arr[0]));

　　createList(newHead, 1, arr);

　　return newHead;

};

var addTwoString = function (str1, str2) {

　　let len1 = str1.length - 1, len2 = str2.length - 1;

　　let carry = 0;

　　let res = [];

　　while (len1 >= 0 || len2 >= 0) {

　　let a = len1 >= 0 ? str1.charAt(len1--) - '0' : 0;

　　let b = len2 >= 0 ? str2.charAt(len2--) - '0' : 0;

　　let temp = a + b + carry;

　　if (temp >= 10) {

　　　　carry = Math.floor(temp / 10);//10位

　　　　temp = Math.floor(temp % 10);//个位

　　} else

　　　　carry = 0;

　　res.unshift(temp);

　　if (carry)

　　res.unshift(1);

　　return res.join("");

var createList = function (head, index, arr) {

　　if (index >= arr.length)

　　　　return;

　　let node = new ListNode(parseInt(arr[index]));

　　head.next = node;

　　createList(node, index + 1, arr.concat());