链表两数相加

题目链接

/**
 * 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) {
    if(l1.val == 0&&l2.val==0&&l1.next==null&&l2.next==null){
        return l1
    }
    let carry = 0//相加的结果是否大于10，如果大于，则为0，否则为1
    let head = null//指向返回新链表的头
    let cur = null//指向新链表的尾节点
    while(l1||l2){
        let num1 = l1?l1.val:0//获取链表上的值，当链表2比链表1长的时候，可设置链表1的高阶为0
        let num2 = l2?l2.val:0//同上
        const sum = num1+num2+carry
        if(head == null){
            head = new ListNode(sum%10)
            cur = head
        }
        else{
            cur.next = new ListNode(sum%10)
            cur = cur.next
        }
        if(sum>=10){
            carry = 1
        }
        else{
            carry = 0
        }
        if(l1){
            l1 = l1.next
        }
        if(l2){
            l2 = l2.next
        }
    }
    if(carry){//检测最后一个carry看是否为1
        cur.next = new ListNode(carry)
    }
    return head

};