Swap the two largest elements in a vector

New to Julia
, ,
13

If performance is important we may use this algorithm which will be of O(n)

function swap!(a)
    i_max = argmax(a)
    i_second = argmin(a)
    d = a[i_max] - a[i_second]     # make this difference minimum to get the second max value 
    for i in 1:length(a)
        diff = a[i_max] - a[i]
        if 0 < diff < d
            i_second = i
            d = diff
        end
    end
    a[i_max], a[i_second] = a[i_second], a[i_max]
return a
end

swap!(a)