Given a singly linked list, swap every two adjacent nodes of the linked list. After the swap, return the head of the linked list.

Note: Solve the problem without modifying the values in the list’s nodes. In other words, only the nodes themselves can be changed.

Constraints:

• The number of nodes in the list is in the range $[0, 100]$.
• $0 \leq$ Node.value $\leq 100$

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Note: As an additional challenge, we have intentionally hidden the solution to this puzzle.

Implement your solution in the following coding playground.