2.两数相加.md

2.两数相加

/*
 * @lc app=leetcode.cn id=2 lang=typescript
 *
 * [2] 两数相加
 *
 * https://leetcode-cn.com/problems/add-two-numbers/description/
 *
 * algorithms
 * Medium (40.93%)
 * Likes:    6980
 * Dislikes: 0
 * Total Accepted:    1M
 * Total Submissions: 2.6M
 * Testcase Example:  '[2,4,3]\n[5,6,4]'
 *
 * 给你两个 非空 的链表，表示两个非负的整数。它们每位数字都是按照 逆序 的方式存储的，并且每个节点只能存储 一位 数字。
 *
 * 请你将两个数相加，并以相同形式返回一个表示和的链表。
 *
 * 你可以假设除了数字 0 之外，这两个数都不会以 0 开头。
 *
 *
 *
 * 示例 1：
 *
 *
 * 输入：l1 = [2,4,3], l2 = [5,6,4]
 * 输出：[7,0,8]
 * 解释：342 + 465 = 807.
 *
 *
 * 示例 2：
 *
 *
 * 输入：l1 = [0], l2 = [0]
 * 输出：[0]
 *
 *
 * 示例 3：
 *
 *
 * 输入：l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
 * 输出：[8,9,9,9,0,0,0,1]
 *
 *
 *
 *
 * 提示：
 *
 *
 * 每个链表中的节点数在范围 [1, 100] 内
 * 0
 * 题目数据保证列表表示的数字不含前导零
 *
 *
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * class ListNode {
 *     val: number
 *     next: ListNode | null
 *     constructor(val?: number, next?: ListNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.next = (next===undefined ? null : next)
 *     }
 * }
 */
function addTwoNumbers(l1: ListNode | null, l2: ListNode | null): ListNode | null {}
// @lc code=end

解法 1: 模拟

class ListNode {
  val: number
  next: ListNode | null
  constructor(val?: number, next?: ListNode | null) {
    this.val = val === undefined ? 0 : val
    this.next = next === undefined ? null : next
  }
}

function addTwoNumbers(l1: ListNode | null, l2: ListNode | null): ListNode | null {
  let pre = 0
  let root: ListNode | null = null
  let node: ListNode | null = null
  while (l1 || l2 || pre) {
    const num = pre + (l1?.val ?? 0) + (l2?.val ?? 0)
    const cur = new ListNode(num % 10)
    pre = Math.floor(num / 10)
    if (!node) {
      root = node = cur
    } else {
      node.next = cur
      node = cur
    }
    if (l1) l1 = l1.next
    if (l2) l2 = l2.next
  }
  return root
}

Case

test.each([
  { input: { l1: [2, 4, 3], l2: [5, 6, 4] }, output: [7, 0, 8] },
  { input: { l1: [0], l2: [0] }, output: [0] },
  { input: { l1: [9, 9, 9, 9, 9, 9, 9], l2: [9, 9, 9, 9] }, output: [8, 9, 9, 9, 0, 0, 0, 1] },
])('input: l1 = $input.l1, l2 = $input.l2', ({ input: { l1, l2 }, output }) => {
  expect(addTwoNumbers(LinkedList.deserialize(l1), LinkedList.deserialize(l2))).toEqual(LinkedList.deserialize(output))
})