Different countries have different boards who classify movies and assign ratings, often with different criteria for determining which rating it should receive and sometimes requiring scenes to be cut or otherwise modified to allow the film to receive a rating at all. See, for example, this question about the cuts made to Deadpool to make it suitable for showing in India.
To make matters even more complicated, there's no universal system of ratings, so an R-rated movie in the US isn't going to have an R rating in the UK (because no such rating exists). Fortunately, the Wikipedia page on Motion picture rating system has a handy comparison table.
From that you can see that the US R rating roughly corresponds to the Swedish "Not approved" rating, which is suitable for viewers aged 15 and above. The section on Sweden further down the page seems to back this up, and suggests that "Not approved" (for children) is the same thing as "15", which is the highest rating given.
With all that information, I'd assume that you'll see the uncensored cinematic release of Deadpool in Sweden (i.e. the same version that was released under an R rating in the US). As additional, anecdotal evidence, Deadpool has a 15 rating in the UK too, and having seen the film I can't imagine there's anything that was removed from the US R-rated version, since it contains a LOT of violence, blood, nudity and strong language.
