将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
示例:
输入:1->2->4, 1->3->4 输出:1->1->2->3->4->4
func mergeTwoLists1(l1 *ListNode, l2 *ListNode) *ListNode {
if l1 == nil {
return l2
}
if l2 == nil {
return l1
}
ret := &ListNode{}
if l1.Val <= l2.Val {
ret = l1
ret.Next = mergeTwoLists1(l1.Next, l2)
} else {
ret = l2
ret.Next = mergeTwoLists1(l1, l2.Next)
}
return ret
}
func mergeTwoLists2(l1 *ListNode, l2 *ListNode) *ListNode {
head := &ListNode{}
ret := head
for l1 != nil && l2 != nil {
if l1.Val < l2.Val {
ret.Next = l1
l1 = l1.Next
} else {
ret.Next = l2
l2 = l2.Next
}
ret = ret.Next
}
if l1 != nil {
ret.Next = l1
}
if l2 != nil {
ret.Next = l2
}
return head.Next
}