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23. Merge k Sorted Lists #31
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92 changes: 92 additions & 0 deletions
src/0023_merge_k_sorted_lists/mksl.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,92 @@ | ||
| /* | ||
| 23. Merge k Sorted Lists | ||
| https://leetcode.com/problems/merge-k-sorted-lists/ | ||
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| Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. | ||
| */ | ||
| // time: 2019年01月02日 | ||
|
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| package mksl | ||
|
|
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| import ( | ||
| "sort" | ||
| ) | ||
|
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| // ListNode Definition for singly-linked list. | ||
| type ListNode struct { | ||
| Val int | ||
| Next *ListNode | ||
| } | ||
|
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| // heap | ||
| // time complexity: O(n log n), where n is len of all lists, the main complexity is sort. | ||
| // space complexity: O(n), where n is len of all lists. | ||
| func mergeKLists(lists []*ListNode) *ListNode { | ||
| for i := 0; i < len(lists); { | ||
| if lists[i] == nil { | ||
| lists = append(lists[0:i], lists[i+1:]...) | ||
| } else { | ||
| i++ | ||
| } | ||
| } | ||
| if 0 == len(lists) { | ||
| return nil | ||
| } | ||
|
|
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| head := &ListNode{} | ||
| cur := head | ||
| for len(lists) > 0 { | ||
| for i := (len(lists) - 1) / 2; i >= 0; i-- { | ||
| shiftUp(lists, len(lists), i) | ||
| } | ||
| cur.Next = &ListNode{Val: lists[0].Val} | ||
| cur = cur.Next | ||
| lists[0] = lists[0].Next | ||
| if lists[0] == nil { | ||
| lists = lists[1:] | ||
| } | ||
| } | ||
| return head.Next | ||
| } | ||
|
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| // build heap | ||
| func shiftUp(lists []*ListNode, n int, k int) { | ||
| for 2*k+1 < n { | ||
| j := 2*k + 1 | ||
| if j+1 < n && lists[j+1].Val < lists[j].Val { | ||
| j = j + 1 | ||
| } | ||
| if lists[k].Val < lists[j].Val { | ||
| break | ||
| } | ||
|
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| lists[j], lists[k] = lists[k], lists[j] | ||
| k = j | ||
| } | ||
| } | ||
|
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| // brute force | ||
| // time complexity: O(n log n), where n is len of all lists, the main complexity is sort. | ||
| // space complexity: O(2n), where n is len of all lists. | ||
| func mergeKLists1(lists []*ListNode) *ListNode { | ||
| nodes := make([]int, 0) | ||
| head := &ListNode{} | ||
| pointer := head | ||
|
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| for _, j := range lists { | ||
| for { | ||
| if j != nil { | ||
| nodes = append(nodes, j.Val) | ||
| j = j.Next | ||
| } else { | ||
| break | ||
| } | ||
| } | ||
| } | ||
| sort.Ints(nodes) | ||
| for _, j := range nodes { | ||
| pointer.Next = &ListNode{Val: j} | ||
| pointer = pointer.Next | ||
| } | ||
| return head.Next | ||
| } |
86 changes: 86 additions & 0 deletions
src/0023_merge_k_sorted_lists/mksl_test.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,86 @@ | ||
| package mksl | ||
|
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| import ( | ||
| "reflect" | ||
| "testing" | ||
| ) | ||
|
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| func TestMergeKLists(t *testing.T) { | ||
| testCases := [][]*ListNode{ | ||
| { | ||
| createSingleList([]int{1, 4, 5}), | ||
| createSingleList([]int{2, 3, 4}), | ||
| createSingleList([]int{4, 6}), | ||
| }, | ||
| { | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{4, 5}), | ||
| createSingleList([]int{}), | ||
| }, | ||
| { | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{}), | ||
| }, | ||
| { | ||
| createSingleList([]int{1, 4, 5}), | ||
| createSingleList([]int{1, 3, 4}), | ||
| createSingleList([]int{2, 6}), | ||
| }, | ||
| } | ||
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| expected := []*ListNode{ | ||
| createSingleList([]int{1, 2, 3, 4, 4, 4, 5, 6}), | ||
| createSingleList([]int{4, 5}), | ||
| nil, | ||
| createSingleList([]int{1, 1, 2, 3, 4, 4, 5, 6}), | ||
| } | ||
|
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| for index, lists := range testCases { | ||
| if res := mergeKLists(lists); !reflect.DeepEqual(res, expected[index]) { | ||
| t.Errorf("expected %v, got %v", expected[index], res) | ||
| } | ||
| } | ||
| } | ||
|
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| func TestMergeKLists1(t *testing.T) { | ||
| testCases := [][]*ListNode{ | ||
| { | ||
| createSingleList([]int{1, 4, 5}), | ||
| createSingleList([]int{1, 3, 4}), | ||
| createSingleList([]int{2, 6}), | ||
| }, | ||
| { | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{4, 5}), | ||
| createSingleList([]int{}), | ||
| }, | ||
| { | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{}), | ||
| createSingleList([]int{}), | ||
| }, | ||
| } | ||
|
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| expected := []*ListNode{ | ||
| createSingleList([]int{1, 1, 2, 3, 4, 4, 5, 6}), | ||
| createSingleList([]int{4, 5}), | ||
| nil, | ||
| } | ||
|
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| for index, lists := range testCases { | ||
| if res := mergeKLists1(lists); !reflect.DeepEqual(res, expected[index]) { | ||
| t.Errorf("expected %v, got %v", expected[index], res) | ||
| } | ||
| } | ||
| } | ||
|
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| func createSingleList(nums []int) *ListNode { | ||
| head := &ListNode{} | ||
| cur := head | ||
| for _, j := range nums { | ||
| cur.Next = &ListNode{Val: j} | ||
| cur = cur.Next | ||
| } | ||
| return head.Next | ||
| } |
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