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92. Reverse Linked List II.cpp
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92. Reverse Linked List II.cpp
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// https://leetcode.com/problems/reverse-linked-list-ii/
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution
{
public:
ListNode *reverseBetween(ListNode *head, int m, int n)
{
ListNode *current = head;
ListNode *previous = nullptr;
while (m > 1)
{
previous = current;
current = current->next;
m--;
n--;
}
ListNode *leftLinkedList = previous;
ListNode *reversedTail = current;
ListNode *next = nullptr;
while (n > 0)
{
next = current->next;
current->next = previous;
previous = current;
current = next;
n--;
}
if (leftLinkedList != nullptr)
leftLinkedList->next = previous;
else
head = previous;
reversedTail->next = current;
return head;
}
};