0092. Reverse Linked List II

Author: coderbean

markdown/0092. Reverse Linked List II.md

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+### [92\. Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)
+
+Difficulty: **Medium**
+
+
+Reverse a linked list from position _m_ to _n_. Do it in one-pass.
+
+**Note: **1 ≤ _m_ ≤ _n_ ≤ length of list.
+
+**Example:**
+
+```
+Input: 1->2->3->4->5->NULL, m = 2, n = 4
+Output: 1->4->3->2->5->NULL
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode reverseBetween(ListNode head, int m, int n) {
+        ListNode fakeNode = new ListNode(-1);
+        fakeNode.next = head;
+        ListNode p = fakeNode;
+        ListNode q = head;
+        int index = 1;
+        while (q.next != null) {
+            if (index >= m && index < n) {
+                ListNode node = q.next;
+                q.next = q.next.next;
+                node.next = p.next;
+                p.next = node;
+            } else {
+                q = q.next;
+            }
+            if (index < m) {
+                p = p.next;
+            }
+            if (++index >= n) {
+                break;
+            }
+        }
+        return fakeNode.next;
+    }
+}
+```
+![pic](https://raw.githubusercontent.com/PicGoBed/PicBed/master/2019-08-14-nLuLW6.jpg)

src/main/java/leetcode/_92_/Main.java

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+package leetcode._92_;
+
+import leetcode.common.ListNode;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        
+        ListNode node1 = new ListNode(1);
+        ListNode node2 = new ListNode(2);
+        ListNode node32 = new ListNode(3);
+        ListNode node41 = new ListNode(4);
+        ListNode node5 = new ListNode(5);
+        node1.next = node2;
+        node2.next = node32;
+        node32.next = node41;
+        node41.next = node5;
+
+        System.out.println(solution.reverseBetween(node1, 2, 4));
+    }
+}
+

src/main/java/leetcode/_92_/Solution.java

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+package leetcode._92_;
+
+import leetcode.common.ListNode;
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode reverseBetween(ListNode head, int m, int n) {
+        ListNode fakeNode = new ListNode(-1);
+        fakeNode.next = head;
+        ListNode p = fakeNode;
+        ListNode q = head;
+        int index = 1;
+        while (q.next != null) {
+            if (index >= m && index < n) {
+                ListNode node = q.next;
+                q.next = q.next.next;
+                node.next = p.next;
+                p.next = node;
+            } else {
+                q = q.next;
+            }
+            if (index < m) {
+                p = p.next;
+            }
+            if (++index >= n) {
+                break;
+            }
+        }
+        return fakeNode.next;
+    }
+}

src/main/java/leetcode/_92_/solution.md

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+### [92\. Reverse Linked List II](https://leetcode.com/problems/reverse-linked-list-ii/)
+
+Difficulty: **Medium**
+
+
+Reverse a linked list from position _m_ to _n_. Do it in one-pass.
+
+**Note: **1 ≤ _m_ ≤ _n_ ≤ length of list.
+
+**Example:**
+
+```
+Input: 1->2->3->4->5->NULL, m = 2, n = 4
+Output: 1->4->3->2->5->NULL
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode reverseBetween(ListNode head, int m, int n) {
+        ListNode fakeNode = new ListNode(-1);
+        fakeNode.next = head;
+        ListNode p = fakeNode;
+        ListNode q = head;
+        int index = 1;
+        while (q.next != null) {
+            if (index >= m && index < n) {
+                ListNode node = q.next;
+                q.next = q.next.next;
+                node.next = p.next;
+                p.next = node;
+            } else {
+                q = q.next;
+            }
+            if (index < m) {
+                p = p.next;
+            }
+            if (++index >= n) {
+                break;
+            }
+        }
+        return fakeNode.next;
+    }
+}
+```
+![pic](https://raw.githubusercontent.com/PicGoBed/PicBed/master/2019-08-14-nLuLW6.jpg)