Follow

Follow

·Jul 13, 2022

# 708. Insert into a Sorted Circular Linked List

## 題目敘述

Given a Circular Linked List node, which is sorted in ascending order, write a function to insert a value `insertVal` into the list such that it remains a sorted circular list. The given node can be a reference to any single node in the list and may not necessarily be the smallest value in the circular list.

If there are multiple suitable places for insertion, you may choose any place to insert the new value. After the insertion, the circular list should remain sorted.

If the list is empty (i.e., the given node is `null`), you should create a new single circular list and return the reference to that single node. Otherwise, you should return the originally given node.

Example 1:

``````Input: head = [3,4,1], insertVal = 2
Output: [3,4,1,2]
Explanation: In the figure above, there is a sorted circular list of three elements. You are given a reference to the node with value 3, and we need to insert 2 into the list. The new node should be inserted between node 1 and node 3. After the insertion, the list should look like this, and we should still return node 3.
``````

Example 2:

``````Input: head = [], insertVal = 1
Output: [1]
Explanation: The list is empty (given head is null). We create a new single circular list and return the reference to that single node.
``````

Example 3:

``````Input: head = [1], insertVal = 0
Output: [1,0]
``````

Constraints:

• The number of nodes in the list is in the range `[0, 5 * 10**4]`.
• `-10**6 <= Node.val, insertVal <= 10**6`

## 解法解析

### 解法範例

#### Go

``````/**
* Definition for a Node.
* type Node struct {
*     Val int
*     Next *Node
* }
*/

func insert(aNode *Node, x int) *Node {
if aNode == nil {
newNode := Node{x, nil}
newNode.Next = &newNode
return &newNode
}

var prev, curr *Node = aNode, aNode.Next
for curr != aNode {
if prev.Val <= x && x <= curr.Val {
break
}
if prev.Val > curr.Val {
if x >= prev.Val || x <= curr.Val {
break
}
}
prev, curr = curr, curr.Next
}

prev.Next = &Node{x, curr}
return aNode
}
``````

#### JavaScript

``````/**
* // Definition for a Node.
* function Node(val, next) {
*     this.val = val;
*     this.next = next;
* };
*/

/**
* @param {number} insertVal
* @return {Node}
*/
var insert = function (head, insertVal) {
const newNode = new Node(insertVal, null);
newNode.next = newNode;
return newNode;
}

if (prev.val <= insertVal && insertVal <= curr.val) {
break;
}
if (prev.val > curr.val && (insertVal >= prev.val || insertVal <= curr.val)) {
break;
}
[prev, curr] = [curr, curr.next];
}

prev.next = new Node(insertVal, curr);
};
``````

#### Kotlin

``````/**
* Definition for a Node.
* class Node(var `val`: Int) {
*     var next: Node? = null
* }
*/

class Solution {
fun insert(head: Node?, insertVal: Int): Node? {
val newNode: Node? = Node(insertVal)
newNode?.next = newNode
return newNode
}

if (prev!!.`val` <= insertVal && insertVal <= curr!!.`val`) {
break
}
if (prev!!.`val` > curr!!.`val`) {
if (insertVal >= prev!!.`val` || insertVal <= curr!!.`val`) {
break
}
}

prev = curr
curr = curr?.next
}

val newNode: Node? = Node(insertVal)
newNode?.next = curr
prev?.next = newNode
}
}
``````

#### PHP

``````/**
* Definition for a Node.
* class Node {
*     public \$val = null;
*     public \$next = null;
*     function __construct(\$val = 0) {
*         \$this->val = \$val;
*         \$this->next = null;
*     }
* }
*/

class Solution
{
/**
* @param Node \$root
* @param Integer \$insertVal
* @return Node
*/
{
\$node = new Node(\$insertVal);
\$node->next = \$node;
return \$node;
}

if (\$prev->val <= \$insertVal && \$insertVal <= \$curr->val) {
break;
}
if (\$prev->val > \$curr->val && (\$insertVal >= \$prev->val || \$insertVal <= \$curr->val)) {
break;
}
\$prev = \$curr;
\$curr = \$curr->next;
}

\$node = new Node(\$insertVal);
\$node->next = \$curr;
\$prev->next = \$node;
}
}
``````

#### Python

``````"""
# Definition for a Node.
class Node:
def __init__(self, val=None, next=None):
self.val = val
self.next = next
"""

class Solution:
def insert(self, head: "Optional[Node]", insertVal: int) -> "Node":

newNode = Node(insertVal, None)
newNode.next = newNode
return newNode

if prev.val <= insertVal <= curr.val:
# Case #1.
break
if prev.val > curr.val:
# Case #2. where we locate the tail element
# 'prev' points to the tail, i.e. the largest element!
if insertVal >= prev.val or insertVal <= curr.val:
break
prev, curr = curr, curr.next
# Case #3.
# did not insert the node in the loop
prev.next = Node(insertVal, curr)
``````

#### Rust

``````
``````

#### Swift

``````/**
* Definition for a Node.
* public class Node {
*     public var val: Int
*     public var next: Node?
*     public init(_ val: Int) {
*         self.val = val
*         self.next = nil
*     }
* }
*/

class Solution {
func insert(_ head: Node?, _ insertVal: Int) -> Node? {
let newNode: Node? = Node(insertVal)
newNode.next = newNode
return newNode
}

if prev!.val <= insertVal && insertVal <= curr!.val {
break
}
if prev!.val > curr!.val {
if insertVal >= prev!.val || insertVal <= curr!.val {
break
}
}
prev = curr
curr = curr?.next
}

var newNode: Node? = Node(insertVal)
newNode.next = curr
prev?.next = newNode