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➤微信公众号：山青咏芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：https://www.cnblogs.com/strengthen/p/9891419.html
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Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.
Example:
Input: [ 1->4->5, 1->3->4, 2->6 ] Output: 1->1->2->3->4->4->5->6
合并 k 个排序链表，返回合并后的排序链表。请分析和描述算法的复杂度。
示例:
输入: [ 1->4->5, 1->3->4, 2->6 ] 输出: 1->1->2->3->4->4->5->6
64ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 15 if lists.count == 0 { 16 return nil 17 } 18 var ar = [Int]() 19 20 for i in 0..<lists.count { 21 var node = lists[i] 22 23 while node != nil { 24 ar.append(node!.val) 25 node = node!.next 26 } 27 } 28 29 if ar.count == 0 { 30 return nil 31 } 32 33 ar = ar.sorted() 34 35 var head = ListNode(ar[0]) 36 var node = head 37 for i in 1..<ar.count { 38 node.next = ListNode(ar[i]) 39 node = node.next! 40 } 41 42 return head 43 } 44 }
76ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 guard !lists.isEmpty else { 15 return nil 16 } 17 18 var values = [Int]() 19 for list in lists { 20 var head = list 21 while head != nil { 22 values.append(head!.val) 23 head = head!.next 24 } 25 } 26 27 values = values.sorted() 28 print(values) 29 let result = ListNode(0) 30 var temp: ListNode? = result 31 for value in values { 32 temp?.next = ListNode(value) 33 temp = temp?.next 34 } 35 36 return result.next 37 } 38 }
84ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 guard !lists.isEmpty else { return nil } 15 guard lists.count > 1 else { return lists[0] } 16 let left = mergeKLists(Array(lists[0..<(lists.count / 2)])) 17 let right = mergeKLists(Array(lists[((lists.count / 2))...])) 18 return mergeTwoLists(left, right) 19 } 20 21 func mergeTwoLists(_ l1: ListNode?, _ l2: ListNode?) -> ListNode? { 22 let prehead = ListNode(-1) 23 var prev: ListNode? = prehead 24 var l1Node: ListNode? = l1 25 var l2Node: ListNode? = l2 26 while let l1 = l1Node, let l2 = l2Node { 27 if l1.val <= l2.val { 28 prev?.next = l1 29 l1Node = l1.next 30 } else { 31 prev?.next = l2 32 l2Node = l2.next 33 } 34 prev = prev?.next 35 } 36 37 prev?.next = l1Node ?? l2Node; 38 39 return prehead.next 40 } 41 }
116ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 guard lists.count > 0 else{ 15 return nil 16 } 17 var left = 0 18 var right = lists.count - 1 19 var _lists = lists 20 while right > 0 { 21 left = 0 22 while left < right { 23 _lists[left] = merge2Lists(_lists[left], _lists[right]) 24 left += 1 25 right -= 1 26 } 27 } 28 return _lists[0] 29 } 30 31 func merge2Lists(_ l1: ListNode?, _ l2: ListNode?) ->ListNode? { 32 let dummy = ListNode(0) 33 var node = dummy 34 35 var l1 = l1 36 var l2 = l2 37 38 while l1 != nil && l2 != nil { 39 if l1!.val < l2!.val { 40 node.next = l1 41 l1 = l1!.next 42 } else { 43 node.next = l2 44 l2 = l2!.next 45 } 46 47 node = node.next! 48 } 49 50 node.next = l1 ?? l2 51 52 return dummy.next 53 } 54 }
120ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 if lists.count == 0 { 15 return nil; 16 } 17 var listArray = [ListNode]() 18 for listNode in lists { 19 var listNode = listNode 20 while listNode != nil { 21 listArray.append(listNode!); 22 listNode = listNode?.next; 23 } 24 } 25 if listArray.count < 1 { 26 if listArray.count == 0 { 27 return nil 28 } else { 29 return listArray[0] 30 } 31 } 32 listArray.sort { (list1, list2) -> Bool in 33 list1.val < list2.val 34 } 35 for index in 0 ..< (listArray.count - 1) { 36 let node = listArray[index] 37 node.next = listArray[index + 1] 38 } 39 let node = listArray[listArray.count - 1] 40 node.next = nil; 41 return listArray[0] 42 } 43 }
124ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 class Solution { 13 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 14 var resultNumbers = [Int]() 15 for linkedList in lists { 16 var currentNode = linkedList 17 while currentNode != nil { 18 resultNumbers.append(currentNode!.val) 19 currentNode = currentNode!.next 20 } 21 } 22 resultNumbers = resultNumbers.sorted() 23 24 var result = ListNode(-1) 25 var currentResultNode = result 26 for num in resultNumbers { 27 currentResultNode.next = ListNode(num) 28 currentResultNode = currentResultNode.next! 29 } 30 31 return result.next 32 } 33 }
140ms
1 /** 2 * Definition for singly-linked list. 3 * public class ListNode { 4 * public var val: Int 5 * public var next: ListNode? 6 * public init(_ val: Int) { 7 * self.val = val 8 * self.next = nil 9 * } 10 * } 11 */ 12 13 class Solution { 14 15 func mergeKLists(_ lists: ArraySlice<ListNode?>) -> ListNode? { 16 let count = lists.endIndex - lists.startIndex 17 guard count > 1 else { return lists.first ?? nil } 18 var nodeOptional1 = lists[lists.startIndex] 19 var nodeOptional2 = lists[lists.startIndex+1] 20 if count > 2 { 21 let midIndex = lists.startIndex + count/2 22 nodeOptional1 = mergeKLists(lists[lists.startIndex..<midIndex]) 23 nodeOptional2 = mergeKLists(lists[midIndex..<lists.endIndex]) 24 } 25 guard var node1 = nodeOptional1, var node2 = nodeOptional2 else { return nodeOptional1 ?? nodeOptional2 } 26 let firstVal = min(node1.val, node2.val) 27 var root = ListNode(firstVal) 28 29 // so that second has a chance 30 let dummieNode = ListNode(0) 31 if node1.val < node2.val { 32 dummieNode.next = node2 33 node2 = dummieNode 34 } else { 35 dummieNode.next = node1 36 node1 = dummieNode 37 } 38 var currentNode = root 39 while let next1 = node1.next, let next2 = node2.next { 40 // print("next vals:", next1.val, next2.val, currentNode!.val) 41 if next1.val < next2.val { 42 let newNode = ListNode(next1.val) 43 currentNode.next = newNode 44 currentNode = newNode 45 node1 = next1 46 } else { 47 let newNode = ListNode(next2.val) 48 currentNode.next = newNode 49 currentNode = newNode 50 node2 = next2 51 } 52 } 53 // print("next:", (node1?.next ?? node2?.next)!.val) 54 currentNode.next = node1.next ?? node2.next 55 return root 56 } 57 58 func mergeKLists(_ lists: [ListNode?]) -> ListNode? { 59 return mergeKLists(lists[lists.startIndex..<lists.endIndex]) 60 } 61 }