Find the Second Largest Element in a Linked List

Given a Linked list of integer data. The task is to write a program that efficiently finds the second largest element present in the Linked List.

Examples:

Input : List = 12 -> 35 -> 1 -> 10 -> 34 -> 1
Output : The second largest element is 34.

Input : List = 10 -> 5 -> 10
Output : The second largest element is 5.

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

A Simple Solution will be to first sort the linked list in descending order and then print the second element from the sorted linked list. The time complexity of this solution is O(nlogn).

A Better Solution is to traverse the Linked list twice. In the first traversal find the maximum element. In the second traversal find the greatest element less than the element obtained in first traversal. The time complexity of this solution is O(n).

A more Efficient Solution can be to find the second largest element in a single traversal.
Below is the complete algorithm for doing this:

1) Initialize two variables first and second to INT_MIN as,
first = second = INT_MIN
2) Start traversing the Linked List,
a) If the current element in Linked List say list[i] is greater
than first. Then update first and second as,
second = first
first = list[i]
b) If the current element is in between first and second,
then update second to store the value of current variable as
second = list[i]
3) Return the value stored in second node.

Below is the implementation of the above approach:

C#

Output:

The second largest element is 34

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