# Check if linked list is sorted (Iterative and Recursive)

Given a Linked List, task is to check whether the Linked List is sorted in Descending order or not?

Examples :

```Input  : 8 -> 7 -> 5 -> 2 -> 1
Output : Yes
Explanation :
8 > 7 > 5 > 2 > 1. So, it is sorted in reverse order

Input  : 24 -> 12 -> 9 -> 11 -> 8 -> 2
Output : No
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Iterative Approach : Traverse the linked list from head to end. For every newly encountered element, check node -> data > node -> next -> data. If True, do same for each node else return 0 and Print “No”.

## C++

 `// C++ program to check Linked List is sorted ` `// in descending order or not ` `#include ` `using` `namespace` `std; ` ` `  `/* Linked list node */` `struct` `Node ` `{ ` `    ``int` `data; ` `    ``struct` `Node* next; ` `}; ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not ` `bool` `isSortedDesc(``struct` `Node *head) ` `{  ` `    ``if` `(head == NULL) ` `        ``return` `true``; ` ` `  `    ``// Traverse the list till last node and return ` `    ``// false if a node is smaller than or equal ` `    ``// its next. ` `    ``for` `(Node *t=head; t->next != NULL; t=t->next) ` `       ``if` `(t->data <= t->next->data) ` `            ``return` `false``; ` `    ``return` `true``; ` `} ` ` `  `Node *newNode(``int` `data) ` `{ ` `   ``Node *temp = ``new` `Node; ` `   ``temp->next = NULL; ` `   ``temp->data = data; ` `} ` ` `  `// Driver program to test above ` `int` `main() ` `{ ` `    ``struct` `Node *head = newNode(7); ` `    ``head->next = newNode(5); ` `    ``head->next->next = newNode(4); ` `    ``head->next->next->next = newNode(3); ` `        `  `    ``isSortedDesc(head) ? cout << ``"Yes"` `:  ` `                         ``cout << ``"No"``; ` `     `  `    ``return` `0; ` `} `

## Java

 `// Java program to check Linked List is sorted ` `// in descending order or not ` `class` `GFG  ` `{ ` ` `  `/* Linked list node */` `static` `class` `Node ` `{ ` `    ``int` `data; ` `    ``Node next; ` `}; ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not ` `static` `boolean` `isSortedDesc(Node head) ` `{  ` `    ``if` `(head == ``null``) ` `        ``return` `true``; ` ` `  `    ``// Traverse the list till last node and return ` `    ``// false if a node is smaller than or equal ` `    ``// its next. ` `    ``for` `(Node t = head; t.next != ``null``; t = t.next) ` `    ``if` `(t.data <= t.next.data) ` `            ``return` `false``; ` `    ``return` `true``; ` `} ` ` `  `static` `Node newNode(``int` `data) ` `{ ` `    ``Node temp = ``new` `Node(); ` `    ``temp.next = ``null``; ` `    ``temp.data = data; ` `    ``return` `temp; ` `} ` ` `  `// Driver Code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``Node head = newNode(``7``); ` `    ``head.next = newNode(``5``); ` `    ``head.next.next = newNode(``4``); ` `    ``head.next.next.next = newNode(``3``); ` `         `  `    ``if``(isSortedDesc(head)) ` `        ``System.out.println(``"Yes"``); ` `    ``else` `        ``System.out.println(``"No"``); ` `} ` `} ` ` `  `// This code is contributed by 29AjayKumar `

## Python3

 `# Python program to check Linked List is sorted ` `# in descending order or not ` `''' Linked list Node '''` ` `  `class` `Node: ` `    ``def` `__init__(``self``, data): ` `        ``self``.data ``=` `data; ` `        ``self``.``next` `=` `next``; ` ` `  `# function to Check Linked List is ` `# sorted in descending order or not ` `def` `isSortedDesc(head): ` `    ``if` `(head ``=``=` `None``): ` `        ``return` `True``; ` ` `  `    ``# Traverse the list till last Node and return ` `    ``# False if a Node is smaller than or equal ` `    ``# its next. ` `    ``while``(head.``next` `!``=` `None``): ` `        ``t ``=` `head; ` `        ``if` `(t.data <``=` `t.``next``.data): ` `            ``return` `False``; ` `        ``head ``=` `head.``next` `    ``return` `True``; ` ` `  `def` `newNode(data): ` `    ``temp ``=` `Node(``0``); ` `    ``temp.``next` `=` `None``; ` `    ``temp.data ``=` `data; ` `    ``return` `temp; ` ` `  `# Driver Code ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``head ``=` `newNode(``7``); ` `    ``head.``next` `=` `newNode(``5``); ` `    ``head.``next``.``next` `=` `newNode(``4``); ` `    ``head.``next``.``next``.``next` `=` `newNode(``3``); ` ` `  `    ``if` `(isSortedDesc(head)): ` `        ``print``(``"Yes"``); ` `    ``else``: ` `        ``print``(``"No"``); ` ` `  `# This code is contributed by 29AjayKumar `

## C#

 `// C# program to check Linked List is sorted ` `// in descending order or not ` `using` `System; ` `     `  `class` `GFG  ` `{ ` ` `  `/* Linked list node */` `public` `class` `Node ` `{ ` `    ``public` `int` `data; ` `    ``public` `Node next; ` `}; ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not ` `static` `bool` `isSortedDesc(Node head) ` `{  ` `    ``if` `(head == ``null``) ` `        ``return` `true``; ` ` `  `    ``// Traverse the list till last node and  ` `    ``// return false if a node is smaller than  ` `    ``// or equal to its next. ` `    ``for` `(Node t = head;  ` `              ``t.next != ``null``; t = t.next) ` `    ``if` `(t.data <= t.next.data) ` `            ``return` `false``; ` `    ``return` `true``; ` `} ` ` `  `static` `Node newNode(``int` `data) ` `{ ` `    ``Node temp = ``new` `Node(); ` `    ``temp.next = ``null``; ` `    ``temp.data = data; ` `    ``return` `temp; ` `} ` ` `  `// Driver Code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``Node head = newNode(7); ` `    ``head.next = newNode(5); ` `    ``head.next.next = newNode(4); ` `    ``head.next.next.next = newNode(3); ` `         `  `    ``if``(isSortedDesc(head)) ` `        ``Console.WriteLine(``"Yes"``); ` `    ``else` `        ``Console.WriteLine(``"No"``); ` `} ` `} ` ` `  `// This code is contributed by Rajput-Ji `

Output:

```Yes
```

Time Complexity : O(N), where N is the length of linked list.

Recursive Approach :
Check Recursively that node -> data > node -> next -> data, If not, return 0 that is our terminated condition to come out from recursion else Call Check_List Function Recursively for next node.

## C++

 `// C++ program to recursively check Linked List  ` `// is sorted in descending order or not ` `#include ` `using` `namespace` `std; ` ` `  `/* Linked list node */` `struct` `Node ` `{ ` `    ``int` `data; ` `    ``struct` `Node* next; ` `}; ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not ` `bool` `isSortedDesc(``struct` `Node *head) ` `{  ` `    ``// Base cases ` `    ``if` `(head == NULL || head->next == NULL) ` `        ``return` `true``; ` `     `  `    ``// Check first two nodes and recursively ` `    ``// check remaining.    ` `    ``return` `(head->data > head->next->data &&  ` `        ``isSortedDesc(head->next)); ` `} ` ` `  `Node *newNode(``int` `data) ` `{ ` `   ``Node *temp = ``new` `Node; ` `   ``temp->next = NULL; ` `   ``temp->data = data; ` `} ` ` `  `// Driver program to test above ` `int` `main() ` `{ ` `    ``struct` `Node *head = newNode(7); ` `    ``head->next = newNode(5); ` `    ``head->next->next = newNode(4); ` `    ``head->next->next->next = newNode(3); ` `        `  `    ``isSortedDesc(head) ? cout << ``"Yes"` `:  ` `                         ``cout << ``"No"``; ` `     `  `    ``return` `0; ` `} `

## Java

 `// Java program to recursively check Linked List  ` `// is sorted in descending order or not  ` `class` `GfG {  ` ` `  `/* Linked list node */` `static` `class` `Node  ` `{  ` `    ``int` `data;  ` `    ``Node next;  ` `} ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not  ` `static` `boolean` `isSortedDesc(Node head)  ` `{  ` `    ``// Base cases  ` `    ``if` `(head == ``null` `|| head.next == ``null``)  ` `        ``return` `true``;  ` `     `  `    ``// Check first two nodes and recursively  ` `    ``// check remaining.  ` `    ``return` `(head.data > head.next.data && isSortedDesc(head.next));  ` `}  ` ` `  `static` `Node newNode(``int` `data)  ` `{  ` `Node temp = ``new` `Node();  ` `temp.next = ``null``;  ` `temp.data = data; ` `return` `temp; ` `}  ` ` `  `// Driver program to test above  ` `public` `static` `void` `main(String[] args)  ` `{  ` `    ``Node head = newNode(``7``);  ` `    ``head.next = newNode(``5``);  ` `    ``head.next.next = newNode(``4``);  ` `    ``head.next.next.next = newNode(``3``);  ` `         `  `    ``if``(isSortedDesc(head) == ``true``) ` `    ``System.out.println(``"Yes"``);  ` `    ``else` `    ``System.out.println(``"No"``);  ` `     `  `} ` `}  `

## C#

 `// C# program to recursively check Linked List  ` `// is sorted in descending order or not  ` `using` `System; ` ` `  `class` `GfG  ` `{  ` ` `  `/* Linked list node */` `public` `class` `Node  ` `{  ` `    ``public` `int` `data;  ` `    ``public` `Node next;  ` `} ` ` `  `// function to Check Linked List is  ` `// sorted in descending order or not  ` `static` `bool` `isSortedDesc(Node head)  ` `{  ` `    ``// Base cases  ` `    ``if` `(head == ``null` `|| head.next == ``null``)  ` `        ``return` `true``;  ` `     `  `    ``// Check first two nodes and recursively  ` `    ``// check remaining.  ` `    ``return` `(head.data > head.next.data &&  ` `                    ``isSortedDesc(head.next));  ` `}  ` ` `  `static` `Node newNode(``int` `data)  ` `{  ` `    ``Node temp = ``new` `Node();  ` `    ``temp.next = ``null``;  ` `    ``temp.data = data; ` `    ``return` `temp; ` `}  ` ` `  `// Driver code ` `public` `static` `void` `Main(String[] args)  ` `{  ` `    ``Node head = newNode(7);  ` `    ``head.next = newNode(5);  ` `    ``head.next.next = newNode(4);  ` `    ``head.next.next.next = newNode(3);  ` `         `  `    ``if``(isSortedDesc(head) == ``true``) ` `    ``Console.WriteLine(``"Yes"``);  ` `    ``else` `    ``Console.WriteLine(``"No"``);  ` `     `  `} ` `} ` ` `  `// This code contributed by Rajput-Ji `

Output:

```Yes
```

Rated as one of the most sought after skills in the industry, own the basics of coding with our C++ STL Course and master the very concepts by intense problem-solving.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.