【LeetCode 0002】【链表】两数相加

1. Add Two Numbers

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 contains a single digit. Add the two numbers and return the sum as a linked list.

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

Example 1:

**Input:** l1 = [2,4,3], l2 = [5,6,4]
**Output:** [7,0,8]
**Explanation:** 342 + 465 = 807.

Example 2:

**Input:** l1 = [0], l2 = [0]
**Output:** [0]

Example 3:

**Input:** l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
**Output:** [8,9,9,9,0,0,0,1]

Constraints:

• The number of nodes in each linked list is in the range [1, 100].
• 0 <= Node.val <= 9
• It is guaranteed that the list represents a number that does not have leading zeros.

Idea

使用头插法构建一个逆序列表
注意进位问题

JavaScript Solution

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers = function(l1, l2) {
    let header = new ListNode(0,null)
    let [val1,val2,carry] = [0,0,0];
    let curr = header
    while(l1||l2||carry){
        if(!l1){
            val1  = 0
        }else{
            val1 = l1.val
            l1 = l1.next
        }
        if(!l2){
            val2  = 0
        }else{
            val2 = l2.val
            l2 = l2.next
        }
        curr.next = new ListNode(((val1+val2+carry)%10),null)
        curr = curr.next
        carry = ~~ ( (val1+val2+carry)/10 )
    }
    return header.next
};