def largestPermutation(k, arr)    
    array_swap = Array.new(arr.length)   
    arr.length.times { |i| array_swap[arr[i]] = i}        
    arr.length.times do |i|
        next if arr[i] == arr.length-i
        if k > 0
            index_change = array_swap[arr.length-i]
            array_swap[arr[i]] = index_change
            arr[i], arr[index_change] = arr[index_change], arr[i]    
            k -= 1
        end        
    end
    arr    
end