# Find the largest and second largest value in a Linked List

Given a Linked List, the task is to find the largest and second largest value in a Linked List.

Example:

Input: LL = 10 -> 15 -> 5 -> 20 -> 7 -> 9
Output:
Largest = 20
Second Largest = 15

Input: LL = 0 -> 5 -> 52 -> 21
Output:
Largest = 52
Second Largest = 21

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

Approach:

1. Store the maximum of first two nodes in a variable max.
2. Store the minimum of first two nodes in a variable second_max.
3. Iterate over the remaining linked list. For each node:
• If current node value is greater than max, then set second_max as max and max as current node’s value.
• Else if current node value is greater than second_max, then set second_max as current node’s value.

Below is the implementation of the above approach:

## C++

 `// C++ program to find the largest and ` `// second largest element in a Linked List ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Link list node ` `struct` `Node { ` `    ``int` `data; ` `    ``struct` `Node* next; ` `}; ` ` `  `// Function to push the node at the ` `// beginning of the linked list ` `void` `push(``struct` `Node** head_ref, ` `          ``int` `new_data) ` `{ ` `    ``struct` `Node* new_node ` `        ``= (``struct` `Node*)``malloc``( ` `            ``sizeof``(``struct` `Node)); ` ` `  `    ``new_node->data = new_data; ` `    ``new_node->next = (*head_ref); ` `    ``(*head_ref) = new_node; ` `} ` ` `  `// Function to print the largest ` `// and second largest element ` `void` `findLargestAndSecondLargest(``struct` `Node* head) ` `{ ` `    ``// initialise max and second max using ` `    ``// first two nodes of linked list ` `    ``int` `val1 = head->data, ` `        ``val2 = head->next->data, ` `        ``max = std::max(val1, val2), ` `        ``second_max = std::min(val1, val2); ` ` `  `    ``// move the head pointer to 3rd node ` `    ``head = head->next->next; ` ` `  `    ``// iterate over rest of linked list ` `    ``while` `(head != NULL) { ` ` `  `        ``if` `(head->data > max) { ` ` `  `            ``// If current node value is greater ` `            ``// than max, then set second_max as ` `            ``// current max value and max as ` `            ``// current node value ` `            ``second_max = max; ` `            ``max = head->data; ` `        ``} ` `        ``else` `if` `(head->data > second_max) { ` ` `  `            ``// else if current node value is ` `            ``// greater than second_max, set ` `            ``// second_max as node value ` `            ``second_max = head->data; ` `        ``} ` ` `  `        ``// move the head pointer to next node ` `        ``head = head->next; ` `    ``} ` ` `  `    ``// Print the largest ` `    ``// and second largest value ` `    ``cout << ``"Largest = "` `         ``<< max << endl; ` `    ``cout << ``"Second Largest = "` `         ``<< second_max << endl; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``struct` `Node* head = NULL; ` ` `  `    ``push(&head, 20); ` `    ``push(&head, 5); ` `    ``push(&head, 15); ` `    ``push(&head, 10); ` `    ``push(&head, 7); ` `    ``push(&head, 6); ` `    ``push(&head, 11); ` `    ``push(&head, 9); ` ` `  `    ``findLargestAndSecondLargest(head); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to find the largest and ` `// second largest element in a Linked List ` `class` `GFG{ ` `  `  `// Link list node ` `static` `class` `Node { ` `    ``int` `data; ` `    ``Node next; ` ` `  `}; ` `  `  `// Function to push the node at the ` `// beginning of the linked list ` `static` `Node push(Node head_ref, ` `          ``int` `new_data) ` `{ ` `    ``Node new_node ` `        ``= ``new` `Node(); ` `  `  `    ``new_node.data = new_data; ` `    ``new_node.next = head_ref; ` `    ``head_ref = new_node; ` `    ``return` `head_ref; ` `} ` `  `  `// Function to print the largest ` `// and second largest element ` `static` `void` `findLargestAndSecondLargest(Node head) ` `{ ` `    ``// initialise max and second max using ` `    ``// first two nodes of linked list ` `    ``int` `val1 = head.data, ` `        ``val2 = head.next.data, ` `        ``max = Math.max(val1, val2), ` `        ``second_max = Math.min(val1, val2); ` `  `  `    ``// move the head pointer to 3rd node ` `    ``head = head.next.next; ` `  `  `    ``// iterate over rest of linked list ` `    ``while` `(head != ``null``) { ` `  `  `        ``if` `(head.data > max) { ` `  `  `            ``// If current node value is greater ` `            ``// than max, then set second_max as ` `            ``// current max value and max as ` `            ``// current node value ` `            ``second_max = max; ` `            ``max = head.data; ` `        ``} ` `        ``else` `if` `(head.data > second_max) { ` `  `  `            ``// else if current node value is ` `            ``// greater than second_max, set ` `            ``// second_max as node value ` `            ``second_max = head.data; ` `        ``} ` `  `  `        ``// move the head pointer to next node ` `        ``head = head.next; ` `    ``} ` `  `  `    ``// Print the largest ` `    ``// and second largest value ` `    ``System.out.print(``"Largest = "` `         ``+ max +``"\n"``); ` `    ``System.out.print(``"Second Largest = "` `         ``+ second_max +``"\n"``); ` `} ` `  `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `    ``Node head = ``null``; ` `  `  `    ``head = push(head, ``20``); ` `    ``head = push(head, ``5``); ` `    ``head = push(head, ``15``); ` `    ``head = push(head, ``10``); ` `    ``head = push(head, ``7``); ` `    ``head = push(head, ``6``); ` `    ``head = push(head, ``11``); ` `    ``head = push(head, ``9``); ` `  `  `    ``findLargestAndSecondLargest(head); ` `} ` `} ` ` `  `// This code is contributed by Rajput-Ji `

## C#

 `// C# program to find the largest and ` `// second largest element in a Linked List ` `using` `System; ` ` `  `class` `GFG{ ` `   `  `// Link list node ` `class` `Node { ` `    ``public` `int` `data; ` `    ``public` `Node next; ` `  `  `}; ` `   `  `// Function to push the node at the ` `// beginning of the linked list ` `static` `Node push(Node head_ref, ` `          ``int` `new_data) ` `{ ` `    ``Node new_node ` `        ``= ``new` `Node(); ` `   `  `    ``new_node.data = new_data; ` `    ``new_node.next = head_ref; ` `    ``head_ref = new_node; ` `    ``return` `head_ref; ` `} ` `   `  `// Function to print the largest ` `// and second largest element ` `static` `void` `findLargestAndSecondLargest(Node head) ` `{ ` `    ``// initialise max and second max using ` `    ``// first two nodes of linked list ` `    ``int` `val1 = head.data, ` `        ``val2 = head.next.data, ` `        ``max = Math.Max(val1, val2), ` `        ``second_max = Math.Min(val1, val2); ` `   `  `    ``// move the head pointer to 3rd node ` `    ``head = head.next.next; ` `   `  `    ``// iterate over rest of linked list ` `    ``while` `(head != ``null``) { ` `   `  `        ``if` `(head.data > max) { ` `   `  `            ``// If current node value is greater ` `            ``// than max, then set second_max as ` `            ``// current max value and max as ` `            ``// current node value ` `            ``second_max = max; ` `            ``max = head.data; ` `        ``} ` `        ``else` `if` `(head.data > second_max) { ` `   `  `            ``// else if current node value is ` `            ``// greater than second_max, set ` `            ``// second_max as node value ` `            ``second_max = head.data; ` `        ``} ` `   `  `        ``// move the head pointer to next node ` `        ``head = head.next; ` `    ``} ` `   `  `    ``// Print the largest ` `    ``// and second largest value ` `    ``Console.Write(``"Largest = "` `         ``+ max +``"\n"``); ` `    ``Console.Write(``"Second Largest = "` `         ``+ second_max +``"\n"``); ` `} ` `   `  `// Driver code ` `public` `static` `void` `Main(String[] args) ` `{ ` `    ``Node head = ``null``; ` `   `  `    ``head = push(head, 20); ` `    ``head = push(head, 5); ` `    ``head = push(head, 15); ` `    ``head = push(head, 10); ` `    ``head = push(head, 7); ` `    ``head = push(head, 6); ` `    ``head = push(head, 11); ` `    ``head = push(head, 9); ` `   `  `    ``findLargestAndSecondLargest(head); ` `} ` `} ` ` `  `// This code is contributed by Princi Singh `

Output:

```Largest = 20
Second Largest = 15
```

Performance Analysis:

• Time Complexity: In the above approach, as we are iterating over the linked list only once, so the time complexity is O(N).
• Auxiliary Space Complexity: In the above approach, we are not using any extra space apart from a few constant size variables, so Auxiliary space complexity is O(1).

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