Question

I wrote an algorithm to find duplicates in a linked-list.
for each node, I iterate from head of the list to the current node, and if it’s a duplicate it is deleted.

what is the complexity of my algorithm?

Answer 1

The complexity of the algorithm is Θ(n^2) worst case, since if there are no dupes, you iterate for each node a linearly increasing number of times, resulting in total of 1 + 2 + .... + n total reads which is Θ(n^2) (from sum of arithmetic progression)

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At best case the complexity is Θ(n) – if all elements are dupes The complexity is Θ(n), because at every iteration the list shrinks, which results in at most 2 node reads per iteration, thus Θ(n)