2两数相加解题记录

哎呀，以为这道题也不用写题解的……结果还是有坑没跳出来。
最开始想法先计算总和再求出链表

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    // 先算出这个值。测试用例会int类型溢出
    total := 0
    wei := 1
    for l1!=nil && l2!=nil {
        total += (l1.Val+l2.Val)*wei // 进位也是正确的
        l1 = l1.Next
        l2 = l2.Next
        wei *= 10
    }

    for l1!=nil {
        total += l1.Val*wei
        l1 = l1.Next
        wei *= 10
    }

    for l2!=nil {
        total += l2.Val*wei
        l2 = l2.Next
        wei *= 10
    }
    fmt.Println(total)

    // 将total转换为链表
    res := &ListNode{}
    curr := res
    for total != 0 {
        // fmt.Println(total)
        curr.Val = total%10
        total /= 10
        if total !=0 {
            curr.Next = &ListNode{}
            curr = curr.Next
        }
    }
    return res
}

var total int64还是会溢出得用big.Int
还是直接链表相加吧，记得保存进位就好了

func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    dummy := &ListNode{}
    curr := dummy
    carry := 0

    for l1 != nil || l2 != nil || carry != 0 {
        sum := carry
        if l1 != nil {
            sum += l1.Val
            l1 = l1.Next
        }
        if l2 != nil {
            sum += l2.Val
            l2 = l2.Next
        }

        carry = sum / 10
        curr.Next = &ListNode{Val: sum % 10}
        curr = curr.Next
    }

    return dummy.Next
}