Algorithm

To check if an element is present in the linked list, traverse the entire list and at every node, check whether the data matches with the specified value. If a match is found, return true, otherwise, after traversing the entire list, return false.

Initialise a temporary pointer to traverse the entire list.
During the traversal, check if the data on the current node matches the specified value. If no match is found, move to the next node.
Continue this traversal until either fast (or next node of fast) reaches null or both the pointers, slow and fast, meet.
At any moment, if the data of the node matches with the val, stop and return true.
If the temporary pointer reaches null without finding the required value, return false.