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Copy path92.反转链表-ii.cpp
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92.反转链表-ii.cpp
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/*
* @lc app=leetcode.cn id=92 lang=cpp
*
* [92] 反转链表 II
*/
#include <iostream>
#include <vector>
using namespace std;
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) {}
};
// @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:
ListNode *reverseBetween(ListNode *head, int m, int n)
{
if (m == n)
return head;
if (head == nullptr)
return head;
int curIdx = 1;
ListNode *newHead = head;
ListNode *pre = nullptr;
ListNode *reHead = nullptr;
ListNode *reTail = nullptr;
ListNode *start = nullptr;
ListNode *end = nullptr;
ListNode *next = nullptr;
while (head)
{
next = head->next;
if (curIdx == m - 1)
{
start = head;
}
if (curIdx == m)
reTail = head;
if (curIdx == n + 1)
end = head;
if (curIdx >= m && curIdx <= n)
{
head->next = pre;
pre = head;
// head = next;
}
curIdx++;
head = next;
}
if (start != nullptr)
start->next = pre;
else
newHead = pre;
if (reTail != nullptr)
reTail->next = end;
return newHead;
}
};
// @lc code=end
int main()
{
Solution s;
// 构建链表;
vector<int> input = {1, 2, 3};
ListNode *head = new ListNode(input[0]);
ListNode *cur = head;
ListNode *pre = nullptr;
for (int i = 1; i < input.size(); i++)
{
cur->next = new ListNode(input[i]);
cur = cur->next;
}
ListNode *newHead = s.reverseBetween(head, 1, 2);
// 输出链表
while (newHead)
{
cout << newHead->val << ' ';
newHead = newHead->next;
}
}