leetcode 日经贴，Cpp code -Reverse Linked List II

bachelorchen

于 2015-05-05 18:30:15 发布

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分类专栏： Cpp leetcode 算法

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本文介绍了如何在给定的链表中反转指定区间的节点，包括定义链表节点结构和实现反转函数。

Reverse Linked List II

/**
 * 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) {
        if (!head || !head->next || m >= n) {
            return head;
        }
        ListNode *cur = head, *pre = NULL;
        int k = n - m;
        while (--m) {
            pre = cur;
            cur = cur->next;
        }
        //reverse
        ListNode *tail = cur;
        ListNode *h = cur;
        cur = cur->next;
        while (cur && k--) {
            ListNode *next = cur->next;
            cur->next = h;
            h = cur;
            cur = next;
        }
        if (pre) {
            pre->next = h;
        } else {
            head = h;
        }
        //after reverse
        tail->next = cur;
        return head;
    }
};