2.Add_Two_Numbers.md

Title

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

Analyze

核心: 根据 sum 的值来决定是否要处理进位

// Keyword: single linked list

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function(l1, l2) {
  let flag = 0
  let head = null,
      temp = null
  while (l1 || l2) {
    let sum = flag
    if (l1) {
      sum += l1.val
      l1 = l1.next
    }

    if (l2) {
      sum += l2.val
      l2 = l2.next
    }

    const list = new ListNode(sum % 10)
    if (head === null) {
      head = list
      temp = list
    } else {
      temp.next = list
      temp = list
    }

    // 处理进位
    flag = 0
    if (sum >= 10) {
      flag = 1
    }
  }

  if (flag === 1) {
    const result = new ListNode(1)
    temp.next = result
    temp = result
  }
  return head
}

Sister Title

445