leetcode 092 Reverse Linked List II

最新推荐文章于 2024-07-17 21:13:48 发布

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本文介绍了一种算法，用于在单次遍历中就地反转链表的指定区间，从位置m到n。提供了完整的C++实现代码，并通过实例演示了如何将链表1->2->3->4->5->NULL中的第2到第4个节点进行反转。

Reverse a linked list from position m to n. Do it in-place and in one-pass.

For example:
Given 1->2->3->4->5->NULL, m = 2 and n = 4,

return 1->4->3->2->5->NULL.

Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤ length of list.

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class Solution {
public:
	ListNode* reverseBetween(ListNode* head, int m, int n) {
		ListNode *lm=head, *pre=NULL, *ln=head, *temp=head;
		for(int i=1; i<=n; i++) {
			if(i < m) {
				pre=lm;
				lm=pre->next;
			}
			ln=temp;
			temp=temp->next;
		}

		ListNode *next=ln->next;

		for(int i=m; i<=n; i++) {
			ListNode *lm_next = lm->next;
			lm->next=next;
			next = lm;
			lm = lm_next;
		}
		
		if(pre!=NULL) {
			pre->next=next;
		} else {
			head = next;
		}

		return head;
	}
}