2_中等_两数相加

2 两数相加

https://leetcode.cn/problems/add-two-numbers/submissions/

算法1：利用伪头节点，开辟空间直接计算。

// date 2022-09-09
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
    if l1 == nil {
        return l2
    }
    if l2 == nil {
        return l1
    }
    dummy := &ListNode{Val: -1}
    pre := dummy
    temp, carry := 0, 0
    n1, n2 := 0, 0
    for l1 != nil || l2 != nil || carry != 0 {
        n1, n2 = 0, 0
        if l1 != nil {
            n1 = l1.Val
            l1 = l1.Next
        }
        if l2 != nil {
            n2 = l2.Val
            l2 = l2.Next
        }
        temp = n1 + n2 + carry
        carry = temp / 10
        pre.Next = &ListNode{Val: temp%10}
        pre = pre.Next
    }
    return dummy.Next
}

算法2：