From 12e58d63aa128e3ceb765b1307ab879e04524bac Mon Sep 17 00:00:00 2001
From: yuanguangxin <yuanguangxin@bytedance.com>
Date: Tue, 21 Jul 2020 18:59:57 +0800
Subject: [PATCH] =?UTF-8?q?add=20q25=5Fk=E4=B8=AA=E4=B8=80=E7=BB=84?=
 =?UTF-8?q?=E7=BF=BB=E8=BD=AC=E9=93=BE=E8=A1=A8?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 README.md                                     |  1 +
 .../q25_k个一组翻转链表/ListNode.java  | 12 ++++++
 .../q25_k个一组翻转链表/Solution.java  | 42 +++++++++++++++++++
 3 files changed, 55 insertions(+)
 create mode 100644 src/链表操作/q25_k个一组翻转链表/ListNode.java
 create mode 100644 src/链表操作/q25_k个一组翻转链表/Solution.java

diff --git a/README.md b/README.md
index 4d014cd..9fa9f93 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@
 
 * [q2_两数相加](/src/链表操作/q2_两数相加)
 * [q19_删除链表的倒数第N个节点](/src/链表操作/q19_删除链表的倒数第N个节点)
+* [q25_k个一组翻转链表](/src/链表操作/q25_k个一组翻转链表)
 * [q61_旋转链表](/src/链表操作/q61_旋转链表)
 * [q138_复制带随机指针的链表](/src/链表操作/q138_复制带随机指针的链表)
 * [q206_反转链表](/src/链表操作/q206_反转链表)
diff --git a/src/链表操作/q25_k个一组翻转链表/ListNode.java b/src/链表操作/q25_k个一组翻转链表/ListNode.java
new file mode 100644
index 0000000..8c6845a
--- /dev/null
+++ b/src/链表操作/q25_k个一组翻转链表/ListNode.java
@@ -0,0 +1,12 @@
+package 链表操作.q25_k个一组翻转链表;
+
+
+public class ListNode {
+    int val;
+    ListNode next;
+
+    ListNode(int x) {
+        val = x;
+    }
+}
+
diff --git a/src/链表操作/q25_k个一组翻转链表/Solution.java b/src/链表操作/q25_k个一组翻转链表/Solution.java
new file mode 100644
index 0000000..991ef41
--- /dev/null
+++ b/src/链表操作/q25_k个一组翻转链表/Solution.java
@@ -0,0 +1,42 @@
+package 链表操作.q25_k个一组翻转链表;
+
+public class Solution {
+
+    public ListNode reverseKGroup(ListNode head, int k) {
+        ListNode hair = new ListNode(0);
+        hair.next = head;
+
+        ListNode pre = hair;
+        ListNode end = hair;
+
+        while (end.next != null) {
+            for (int i = 0; i < k && end != null; i++){
+                end = end.next;
+            }
+            if (end == null){
+                break;
+            }
+            ListNode start = pre.next;
+            ListNode next = end.next;
+            end.next = null;
+            pre.next = reverse(start);
+            start.next = next;
+            pre = start;
+
+            end = pre;
+        }
+        return hair.next;
+    }
+
+    private ListNode reverse(ListNode head) {
+        ListNode pre = null;
+        ListNode curr = head;
+        while (curr != null) {
+            ListNode next = curr.next;
+            curr.next = pre;
+            pre = curr;
+            curr = next;
+        }
+        return pre;
+    }
+}