feat: add python and java solutions to leetcode problem: No.0024

Author: yanglbme

README.md

@@ -58,6 +58,7 @@
 1. [从尾到头打印链表](/lcof/面试题06.%20从尾到头打印链表/README.md)
 1. [删除链表的节点](/lcof/面试题18.%20删除链表的节点/README.md)
 1. [链表中倒数第 k 个节点](/lcci/02.02.Kth%20Node%20From%20End%20of%20List/README.md)
+1. [两两交换链表中的节点](/solution/0000-0099/0024.Swap%20Nodes%20in%20Pairs/README.md)
 1. [合并两个有序链表](/solution/0000-0099/0021.Merge%20Two%20Sorted%20Lists/README.md)
 1. [合并 K 个排序链表](/solution/0000-0099/0023.Merge%20k%20Sorted%20Lists/README.md)
 1. [排序链表](/solution/0100-0199/0148.Sort%20List/README.md)

README_EN.md

@@ -56,6 +56,7 @@ Complete solutions to [LeetCode](https://leetcode-cn.com/problemset/all/), [LCOF
 
 1. [Delete Node in a Linked List](/solution/0200-0299/0237.Delete%20Node%20in%20a%20Linked%20List/README_EN.md)
 1. [Kth Node From End of List](/lcci/02.02.Kth%20Node%20From%20End%20of%20List/README_EN.md)
+1. [Swap Nodes in Pairs](/solution/0000-0099/0024.Swap%20Nodes%20in%20Pairs/README_EN.md)
 1. [Merge Two Sorted Lists](/solution/0000-0099/0021.Merge%20Two%20Sorted%20Lists/README_EN.md)
 1. [Merge k Sorted Lists](/solution/0000-0099/0023.Merge%20k%20Sorted%20Lists/README_EN.md)
 1. [Sort List](/solution/0100-0199/0148.Sort%20List/README_EN.md)

index.html

@@ -35,6 +35,7 @@
       search: [
         '/','/solution/','/lcof/','/lcci/', '/basic/'
       ],
+      loadSidebar: 'summary.md',
       auto2top: true,
       subMaxLevel: 2,
       alias: {

solution/0000-0099/0024.Swap Nodes in Pairs/README.md

@@ -34,9 +34,16 @@
 #         self.next = next
 class Solution:
     def swapPairs(self, head: ListNode) -> ListNode:
-        if head is None or head.next is None:
-            return head
-
+        dummy = ListNode(next=head)
+        pre, cur = dummy, head
+        while cur and cur.next:
+            pre.next = cur.next
+            t = cur.next.next
+            cur.next.next = cur
+            cur.next = t
+            pre = cur
+            cur = cur.next
+        return dummy.next
 ```
 
 ### **Java**
@@ -56,7 +63,17 @@ class Solution:
  */
 class Solution {
     public ListNode swapPairs(ListNode head) {
-
+        ListNode dummy = new ListNode(0, head);
+        ListNode pre = dummy, cur = head;
+        while (cur != null && cur.next != null) {
+            pre.next = cur.next;
+            ListNode t = cur.next.next;
+            cur.next.next = cur;
+            cur.next = t;
+            pre = cur;
+            cur = cur.next;
+        }
+        return dummy.next;
     }
 }
 ```

solution/0000-0099/0024.Swap Nodes in Pairs/README_EN.md

@@ -32,6 +32,16 @@ Given <code>1-&gt;2-&gt;3-&gt;4</code>, you should return the list as <code>2-&g
 #         self.next = next
 class Solution:
     def swapPairs(self, head: ListNode) -> ListNode:
+        dummy = ListNode(next=head)
+        pre, cur = dummy, head
+        while cur and cur.next:
+            pre.next = cur.next
+            t = cur.next.next
+            cur.next.next = cur
+            cur.next = t
+            pre = cur
+            cur = cur.next
+        return dummy.next
 ```
 
 ### **Java**
@@ -49,7 +59,17 @@ class Solution:
  */
 class Solution {
     public ListNode swapPairs(ListNode head) {
-
+        ListNode dummy = new ListNode(0, head);
+        ListNode pre = dummy, cur = head;
+        while (cur != null && cur.next != null) {
+            pre.next = cur.next;
+            ListNode t = cur.next.next;
+            cur.next.next = cur;
+            cur.next = t;
+            pre = cur;
+            cur = cur.next;
+        }
+        return dummy.next;
     }
 }
 ```

solution/0000-0099/0024.Swap Nodes in Pairs/Solution.java

@@ -1,24 +1,25 @@
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
 class Solution {
     public ListNode swapPairs(ListNode head) {
-        if (head == null || head.next == null) {
-            return head;
+        ListNode dummy = new ListNode(0, head);
+        ListNode pre = dummy, cur = head;
+        while (cur != null && cur.next != null) {
+            pre.next = cur.next;
+            ListNode t = cur.next.next;
+            cur.next.next = cur;
+            cur.next = t;
+            pre = cur;
+            cur = cur.next;
         }
-        ListNode pre = head.next;
-        ListNode p = head;
-        ListNode q = head.next;
-        
-        while (q != null) {
-            ListNode t = q.next;
-            q.next = p;
-            if (t == null || t.next == null) {
-                p.next = t;
-                break;
-            }
-            p.next = t.next;
-            p = t;
-            q = p.next;
-        }
-        
-        return pre;
+        return dummy.next;
     }
 }

solution/0000-0099/0024.Swap Nodes in Pairs/Solution.py

@@ -1,28 +1,17 @@
 # Definition for singly-linked list.
 # class ListNode:
-#     def __init__(self, x):
-#         self.val = x
-#         self.next = None
-
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
 class Solution:
-    def swapPairs(self, head):
-        """
-        :type head: ListNode
-        :rtype: ListNode
-        """
-        if (not head) or (not head.next):
-            return head
-        pre=head.next
-        p=head
-        q=head.next
-        
-        while q:
-            t=q.next
-            q.next=p
-            if (not t) or (not t.next):
-                p.next=t
-                break
-            p.next=t.next
-            p=t
-            q=p.next
-        return pre
+    def swapPairs(self, head: ListNode) -> ListNode:
+        dummy = ListNode(next=head)
+        pre, cur = dummy, head
+        while cur and cur.next:
+            pre.next = cur.next
+            t = cur.next.next
+            cur.next.next = cur
+            cur.next = t
+            pre = cur
+            cur = cur.next
+        return dummy.next

solution/0200-0299/0206.Reverse Linked List/README.md

@@ -125,7 +125,7 @@ var reverseList = function (head) {
 
 ### **Go**
 
-```Go
+```go
 func reverseList(head *ListNode) *ListNode {
     if head == nil ||head.Next == nil {
         return head

solution/0200-0299/0206.Reverse Linked List/README_EN.md

@@ -124,7 +124,7 @@ var reverseList = function (head) {
 
 ### **Go**
 
-```Go
+```go
 func reverseList(head *ListNode) *ListNode {
     if head == nil ||head.Next == nil {
         return head

summary.md

@@ -0,0 +1,4 @@
+- 题解速览
+  - [LeetCode（未完）](/solution/README.md)
+  - [LeetCode 《剑指 Offer（第 2 版）》](/lcof/README.md)
+  - [LeetCode 《程序员面试金典（第 6 版）》](/lcci/README.md)

summary_en.md

@@ -0,0 +1,4 @@
+- All Solutions
+  - [LeetCode(Not finished yet)](/solution/README_EN.md)
+  - [LCOF: _Coding Interviews, 2nd Edition_](/lcof/README_EN.md)
+  - [LCCI: _Cracking the Coding Interview, 6th Edition_](/lcci/README_EN.md)