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swapFirstAndLast.md

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Problem statement: Given a doubly linked list. Implement swapFirstLast() that swaps the values of the first and last nodes of doubly linked list.

Examples:

Input: [1,2,3,4,5] Output: [5,2,3,4,1]

Algorithmic Steps This problem is solved by swapping the values of head and tail nodes. The algorithmic approach can be summarized as follows:

  1. Add an edge case returing immediately if the length of the list is less than or equal to 1.

  2. Store the head's value in a temporary variable temp.

  3. Update the head's value with tail's value.

  4. Modify the tail's value with a value stored in temp variable.

  5. Now the list is modified with swapped values of first and last nodes.

Time and Space complexity: This algorithm has a time complexity of O(1). This is because we are just swapping the first and last node values in a list.

Here, we don't use any additional datastructure other than few variables. Hence, the space complexity will be O(1).