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feat: add solutions to lc problem: No.0148 #3904

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merged 1 commit into from
Dec 30, 2024
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feat: add solutions to lc problem: No.0148 #3904

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180 changes: 93 additions & 87 deletions solution/0100-0199/0148.Sort List/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,15 @@ tags:

<!-- solution:start -->

### 方法一
### 方法一：归并排序

我们可以用归并排序的思想来解决。

首先，我们利用快慢指针找到链表的中点，将链表从中点处断开，形成两个独立的子链表 $\textit{l1}$ 和 $\textit{l2}$。

然后，我们递归地对 $\textit{l1}$ 和 $\textit{l2}$ 进行排序，最后将 $\textit{l1}$ 和 $\textit{l2}$ 合并为一个有序链表。

时间复杂度 $O(n \times \log n)$，空间复杂度 $O(\log n)$。其中 $n$ 是链表的长度。

<!-- tabs:start -->

Expand All @@ -80,26 +88,27 @@ tags:
# self.val = val
# self.next = next
class Solution:
def sortList(self, head: ListNode) -> ListNode:
def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]:
if head is None or head.next is None:
return head
slow, fast = head, head.next
while fast and fast.next:
slow, fast = slow.next, fast.next.next
t = slow.next
slow = slow.next
fast = fast.next.next
l1, l2 = head, slow.next
slow.next = None
l1, l2 = self.sortList(head), self.sortList(t)
l1, l2 = self.sortList(l1), self.sortList(l2)
dummy = ListNode()
cur = dummy
tail = dummy
while l1 and l2:
if l1.val <= l2.val:
cur.next = l1
tail.next = l1
l1 = l1.next
else:
cur.next = l2
tail.next = l2
l2 = l2.next
cur = cur.next
cur.next = l1 or l2
tail = tail.next
tail.next = l1 or l2
return dummy.next
```

Expand All @@ -126,23 +135,23 @@ class Solution {
slow = slow.next;
fast = fast.next.next;
}
ListNode t = slow.next;
ListNode l1 = head, l2 = slow.next;
slow.next = null;
ListNode l1 = sortList(head);
ListNode l2 = sortList(t);
l1 = sortList(l1);
l2 = sortList(l2);
ListNode dummy = new ListNode();
ListNode cur = dummy;
ListNode tail = dummy;
while (l1 != null && l2 != null) {
if (l1.val <= l2.val) {
cur.next = l1;
tail.next = l1;
l1 = l1.next;
} else {
cur.next = l2;
tail.next = l2;
l2 = l2.next;
}
cur = cur.next;
tail = tail.next;
}
cur.next = l1 == null ? l2 : l1;
tail.next = l1 != null ? l1 : l2;
return dummy.next;
}
}
Expand All @@ -164,30 +173,33 @@ class Solution {
class Solution {
public:
ListNode* sortList(ListNode* head) {
if (!head || !head->next) return head;
auto* slow = head;
auto* fast = head->next;
if (!head || !head->next) {
return head;
}
ListNode* slow = head;
ListNode* fast = head->next;
while (fast && fast->next) {
slow = slow->next;
fast = fast->next->next;
}
auto* t = slow->next;
ListNode* l1 = head;
ListNode* l2 = slow->next;
slow->next = nullptr;
auto* l1 = sortList(head);
auto* l2 = sortList(t);
auto* dummy = new ListNode();
auto* cur = dummy;
l1 = sortList(l1);
l2 = sortList(l2);
ListNode* dummy = new ListNode();
ListNode* tail = dummy;
while (l1 && l2) {
if (l1->val <= l2->val) {
cur->next = l1;
tail->next = l1;
l1 = l1->next;
} else {
cur->next = l2;
tail->next = l2;
l2 = l2->next;
}
cur = cur->next;
tail = tail->next;
}
cur->next = l1 ? l1 : l2;
tail->next = l1 ? l1 : l2;
return dummy->next;
}
};
Expand All @@ -211,25 +223,27 @@ func sortList(head *ListNode) *ListNode {
for fast != nil && fast.Next != nil {
slow, fast = slow.Next, fast.Next.Next
}
t := slow.Next
l1 := head
l2 := slow.Next
slow.Next = nil
l1, l2 := sortList(head), sortList(t)
l1 = sortList(l1)
l2 = sortList(l2)
dummy := &ListNode{}
cur := dummy
tail := dummy
for l1 != nil && l2 != nil {
if l1.Val <= l2.Val {
cur.Next = l1
tail.Next = l1
l1 = l1.Next
} else {
cur.Next = l2
tail.Next = l2
l2 = l2.Next
}
cur = cur.Next
tail = tail.Next
}
if l1 != nil {
cur.Next = l1
tail.Next = l1
} else {
cur.Next = l2
tail.Next = l2
}
return dummy.Next
}
Expand All @@ -251,32 +265,31 @@ func sortList(head *ListNode) *ListNode {
*/

function sortList(head: ListNode | null): ListNode | null {
if (head == null || head.next == null) return head;
// 快慢指针定位中点
let slow: ListNode = head,
fast: ListNode = head.next;
while (fast != null && fast.next != null) {
slow = slow.next;
if (head === null || head.next === null) {
return head;
}
let [slow, fast] = [head, head.next];
while (fast !== null && fast.next !== null) {
slow = slow.next!;
fast = fast.next.next;
}
// 归并排序
let mid: ListNode = slow.next;
let [l1, l2] = [head, slow.next];
slow.next = null;
let l1: ListNode = sortList(head);
let l2: ListNode = sortList(mid);
let dummy: ListNode = new ListNode();
let cur: ListNode = dummy;
while (l1 != null && l2 != null) {
l1 = sortList(l1);
l2 = sortList(l2);
const dummy = new ListNode();
let tail = dummy;
while (l1 !== null && l2 !== null) {
if (l1.val <= l2.val) {
cur.next = l1;
tail.next = l1;
l1 = l1.next;
} else {
cur.next = l2;
tail.next = l2;
l2 = l2.next;
}
cur = cur.next;
tail = tail.next;
}
cur.next = l1 == null ? l2 : l1;
tail.next = l1 ?? l2;
return dummy.next;
}
```
Expand Down Expand Up @@ -357,32 +370,31 @@ impl Solution {
* @return {ListNode}
*/
var sortList = function (head) {
if (!head || !head.next) {
if (head === null || head.next === null) {
return head;
}
let slow = head;
let fast = head.next;
while (fast && fast.next) {
let [slow, fast] = [head, head.next];
while (fast !== null && fast.next !== null) {
slow = slow.next;
fast = fast.next.next;
}
let t = slow.next;
let [l1, l2] = [head, slow.next];
slow.next = null;
let l1 = sortList(head);
let l2 = sortList(t);
l1 = sortList(l1);
l2 = sortList(l2);
const dummy = new ListNode();
let cur = dummy;
while (l1 && l2) {
let tail = dummy;
while (l1 !== null && l2 !== null) {
if (l1.val <= l2.val) {
cur.next = l1;
tail.next = l1;
l1 = l1.next;
} else {
cur.next = l2;
tail.next = l2;
l2 = l2.next;
}
cur = cur.next;
tail = tail.next;
}
cur.next = l1 || l2;
tail.next = l1 ?? l2;
return dummy.next;
};
```
Expand All @@ -403,37 +415,31 @@ var sortList = function (head) {
*/
public class Solution {
public ListNode SortList(ListNode head) {
if (head == null || head.next == null)
{
if (head == null || head.next == null) {
return head;
}
ListNode slow = head, fast = head.next;
while (fast != null && fast.next != null)
{
while (fast != null && fast.next != null) {
slow = slow.next;
fast = fast.next.next;
}
ListNode t = slow.next;
ListNode l1 = head, l2 = slow.next;
slow.next = null;
ListNode l1 = SortList(head);
ListNode l2 = SortList(t);
l1 = SortList(l1);
l2 = SortList(l2);
ListNode dummy = new ListNode();
ListNode cur = dummy;
while (l1 != null && l2 != null)
{
if (l1.val <= l2.val)
{
cur.next = l1;
ListNode tail = dummy;
while (l1 != null && l2 != null) {
if (l1.val <= l2.val) {
tail.next = l1;
l1 = l1.next;
}
else
{
cur.next = l2;
} else {
tail.next = l2;
l2 = l2.next;
}
cur = cur.next;
tail = tail.next;
}
cur.next = l1 == null ? l2 : l1;
tail.next = l1 != null ? l1 : l2;
return dummy.next;
}
}
Expand Down
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