# 92 - Reverse Linked List II
解法一 - In-place reversal
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* reverseBetween(ListNode* head, int m, int n) {
// Corner cases, return directly
if(head == nullptr or head->next == nullptr or m == n) {
return head;
}
// Prepare dummyHead because m might be 1
ListNode* dummyHead = new ListNode(-1);
dummyHead->next = head;
ListNode* prev = dummyHead;
ListNode* cur = dummyHead->next;
// Move to position m
int i = 1;
while(i < m) {
prev = cur;
cur = cur->next;
++i;
}
// Reverse between m to n
ListNode* node = prev;
while(i <= n) {
ListNode* next = cur->next;
cur->next = prev;
prev = cur;
cur = next;
++i;
}
node->next->next = cur;
node->next = prev;
// Return the next of dummyHead;
return dummyHead->next;
}
};
額外補充
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