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  • Leetcode题目:Swap Nodes in Pairs

    题目:Given a linked list, swap every two adjacent nodes and return its head.

    For example,
    Given 1->2->3->4, you should return the list as 2->1->4->3.

    Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed.

    题目解答:成对的调转链表中的节点。使用指针p和q表示当前待交换的两个节点。o代表了前一个节点。r表示后一个节点。

    代码:

    /**
     * Definition for singly-linked list.
     * struct ListNode {
     *     int val;
     *     ListNode *next;
     *     ListNode(int x) : val(x), next(NULL) {}
     * };
     */
    class Solution {
    public:
        ListNode* swapPairs(ListNode* head) {
            ListNode *Head = new ListNode(-1);
            Head -> next = head;
            ListNode *o = Head;
            ListNode *p = Head -> next;
            while(p != NULL)
            {
                ListNode *q = p -> next;
                if(q != NULL)
                {
                    ListNode *r = q -> next;
                    o -> next = q;
                    q -> next = p;
                    p -> next = r;
                    o = o -> next -> next;
                }
                p = p -> next;
            }
            p = Head -> next;
            delete Head;
            return p;
        }
    };

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  • 原文地址:https://www.cnblogs.com/CodingGirl121/p/5425505.html
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