reorder-list

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题目描述

Given a singly linked list L: L0→L1→…→Ln-1→Ln,
reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…

You must do this in-place without altering the nodes' values.

For example,
Given{1,2,3,4}, reorder it to{1,4,2,3}.

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代码

语言：C++ 运行时间： <1 ms 占用内存：9740K 状态：答案正确

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
classSolution {
public:
    voidreorderList(ListNode *head) {
        if(!head || !head->next) return;
        vector<int> v;
        ListNode* p = head;
        while(p){
            v.push_back(p->val);
            p = p->next;
        }
        p = head;
        inti = 0,j = v.size()-1,index = 0;
        while(i<=j){
            if(index%2==0){
                p->val = v[i++];
            }else{
                p->val = v[j--];
            }
            p = p->next;
            ++index;
        }
    }
};

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