007.两数相加

• 2.两数相加

两数相加 - 原地相加

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
	head := l1
	prev := l1
	carry := 0
	for l1 != nil && l2 != nil {
		l1.Val += l2.Val + carry
		if l1.Val >= 10 {
			l1.Val -= 10
			carry = 1
		} else {
			carry = 0
		}
		prev = l1
		l1 = l1.Next
		l2 = l2.Next
	}
 
	if l2 != nil {
		prev.Next = l2
		l1 = l2
	}
	for l1 != nil {
		l1.Val += carry
		if l1.Val >= 10 {
			l1.Val -= 10
			carry = 1
		} else {
			carry = 0
			break
		}
		prev = l1
		l1 = l1.Next
	}
 
	if carry != 0 {
		prev.Next = &ListNode{ Val: carry }
	}
 
	return head
}