Occurence of an integer in a Linked List

Difficulty Level : Difficulty: Easy

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Given a singly linked list and a key, count the number of occurrences of the given key in the linked list.

Examples:

Input: Linked List: 1->2->1->2->1->3->1, key = 1

Output: 4
Explanation: 1 appears 4 times. 

Input: Linked List: 1->2->1->2->1, key = 3

Output: 0
Explanation: 3 appears 0 times.

Expected Time Complexity: O(n)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ number of nodes, key ≤ 10⁵
1 ≤ data of node ≤ 10⁵

Topic Tags :
Linked List Data Structures