Mergesort with $O(n^2 \log n)$ runtime I have a task where i need to find a problem in which mergesort has to have a runtime of $O(n^2 \log n)$. In our lecture we said that the runtime is $O(n \log n)$ assuming that every comparison is $O(1)$. I think that I have to work with comparison-complexity but I dont know how to create a runtime of $O(n^2 \log n)$ since mergesort has best and worst-case complexity of $O(n \log n)$. Could anybody help me out creating a problem to achieve a runtime of $O(n^2 \log n)$ ?
Remember what $O(\cdot)$ means. You don't need to do anything. Mergesort has a running time of $O(n\log n)$ which is already $O(n^2 \log n)$, $O(2^n)$ and $O(\text{any larger function you want})$.