Since your amount is big, try to negotiate with your home bank to get a good exchange rate. Before you do this, you may ask a few other banks
about their rate. Then, ask your home bank to have a match.
I think they are trying to divert the attention of other people to its current problem. US did this to Japan and Germany before. The result is that these two countries have exported even more ever since.
sort two arrays with merge sort: running time n log(n)
compare all elements one by one in two arrays: running time n
Total running time is n log(n)
No extra memory is needed.