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143-重排链表.cpp
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143-重排链表.cpp
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/*
* @lc app=leetcode.cn id=143 lang=cpp
*
* [143] 重排链表
*/
// @lc code=start
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution
{
public:
void reorderList(ListNode* head)
{
if (!head || !head->next || !head->next->next)
return;
auto* slow = head;
auto* fast = head->next;
while (fast && fast->next) {
slow = slow->next;
fast = fast->next->next;
}
ListNode* n = slow->next;
slow->next = nullptr;
ListNode* pre = nullptr;
ListNode* cur = n;
while (cur) {
n = cur->next;
cur->next = pre;
pre = cur;
cur = n;
}
cur = head;
while (cur && pre) {
n = cur->next;
slow = pre->next;
cur->next = pre;
pre->next = n;
pre = slow;
cur = n;
}
return;
}
};
// @lc code=end