题解 | #两个链表生成相加链表#

 * function ListNode(x){
 *   this.val = x;
 *   this.next = null;
 * }
 */

/**
 * 
 * @param head1 ListNode类 
 * @param head2 ListNode类 
 * @return ListNode类
 */
function ReverseList(pHead)
{
    // write code here
    if(!pHead || !pHead.next){
        return pHead
    }
    let len = 0
    let pre = null
    let cur = null
    while(pHead){
        cur = pHead.next
        pHead.next = pre
        pre = pHead
        pHead = cur
        len++
    }
    return [pre,len]
}

function addInList( head1 ,  head2 ) {
    // write code here
    let [h1,len1] = ReverseList(head1)
    let [h2,len2] = ReverseList(head2)
    if(len2 > len1)
        [h1,h2] = [h2,h1]
    let carry = 0,num = 0
    let resHead = h1
    while(h2){
        num = h1.val + h2.val + carry
        h1.val = num % 10
        carry = Math.floor(num/10)
        h2 = h2.next
        if(h2){
            h1 = h1.next
        }
    }
    while(carry){
        if(h1.next){
            h1 = h1.next
            num = h1.val + carry
            h1.val = num % 10
            carry = Math.floor(num/10)
        }else{
            h1.next = new ListNode(1)
            carry = 0
        }
    }
    let [res,n] = ReverseList(resHead)
    return res
}
module.exports = {
    addInList : addInList
};