题目描述：
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| import Foundation
class For17Solution {
func mergeListNode(_ head1: ListNode?,_ head2: ListNode?) -> ListNode? {
if head1 == nil {
return head2
}
if head2 == nil {
return head1
}
var newHead : ListNode? = nil
var pHead = head1
var qHead = head2
if pHead!.val < qHead!.val {
newHead = pHead
pHead = pHead?.next
}else {
newHead = qHead
qHead = qHead?.next
}
var tempHead = newHead
while pHead != nil && qHead != nil {
if pHead!.val < qHead!.val {
tempHead?.next = pHead
pHead = pHead?.next
}else {
tempHead?.next = qHead
qHead = qHead?.next
}
tempHead = tempHead?.next
}
if pHead != nil {
tempHead?.next = pHead
}
if qHead != nil {
tempHead?.next = qHead
}
return newHead
}
func mergeListNode2(_ head1: ListNode?,_ head2: ListNode?) -> ListNode? {
if head1 == nil {
return head2
}
if head2 == nil {
return head1
}
var newHead: ListNode? = nil
if head1!.val < head2!.val {
newHead = head1
newHead?.next = mergeListNode2(head1?.next, head2)
}else {
newHead = head2
newHead?.next = mergeListNode2(head1, head2?.next)
}
return newHead
}
}
|
算法思想：有点类似合并两个排序数组。递归的话，相对好理解一点。
github地址：https://github.com/cubegao/LeetCode
