From 4dc82bd55c4eec324ab57c55b2abe515a3fe1910 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=94=90=E6=A0=91=E6=A3=AE?= <tangshusen@pku.edu.cn>
Date: Sun, 24 Mar 2019 23:39:01 +0800
Subject: [PATCH] Create 92. Reverse Linked List II.md

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+# [92. Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)
+# 思路
+首先还是开辟一个真正的头结点real_head, 其next指针指向head。然后向后移动`m - 1`步到达需要翻转的第一个节点的前一个节点，记为pre，如果按照下面的例子的话
+pre就指向1，然后我们翻转pre后面的`n-m`个节点即可。
+```
+Input: 1->2->3->4->5->NULL, m = 2, n = 4
+Output: 1->4->3->2->5->NULL
+```
+
+# C++
+``` C++
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int m, int n) {
+        ListNode *real_head = new ListNode(0);
+        real_head -> next = head;
+        ListNode *p, *pre = real_head, *tmp;
+        n -= m;
+        while(--m) pre = pre -> next;
+        p = pre -> next;
+        
+        // reverse n-m nodes
+        while(n--){
+            tmp = p -> next;
+            p -> next = tmp -> next;
+            tmp -> next = pre -> next;
+            pre -> next = tmp;   
+        }
+        return real_head -> next;
+    }
+};
+```