import copy
begining = [False,False,False,False,False,None,True,True,True,True,True]
#False = black True = white
its = [0]
def swap(layout, step):
    layoutCopy = copy.deepcopy(layout)
    layoutCopy[(step[0]+step[1])], layoutCopy[step[1]] = layoutCopy[step[1]], layoutCopy[(step[0]+step[1])]
    return layoutCopy
def isSolved(layout):
    for i in range(len(layout)):
        if(layout[i] == False):
            return (i >= (len(layout)/2))
def recurse(layout, its, steps = []):
    if isSolved(layout):
        its[0] += 1
        print(layout,list(x[0] for x in steps))
        return
    step = None
    for i in range(len(layout)):
        if(layout[i] == None):
            if(i >= 1): #If the empty space could have something to the left
                if(layout[i - 1] == False):
                    step = [-1,i]
                    recurse(swap(layout,step), its, (steps+[step]))
                if(i > 1): #If the empty space could have something 2 to the left
                    if(layout[i - 2] == False):
                        step = [-2,i]
                        recurse(swap(layout,step), its, (steps+[step]))
            if(i < (len(layout)-1)): #If the empty space could have something to the right
                if(layout[i + 1] == True):
                    step = [1,i]
                    recurse(swap(layout,step), its, (steps+[step]))
                if(i < (len(layout)-2)): #If the empty space could have something to the right
                    if(layout[i + 2] == True):
                        step = [2,i]
                        recurse(swap(layout,step), its, (steps+[step]))
    its[0] += 1
    #return None
recurse(begining,its,[])
print(its[0])

# Python program for implementation of Radix Sort
	
# A function to do counting sort of arr[] according to
# the digit represented by exp.
def countingSort(arr, exp1):
	
	n = len(arr)
	
	# The output array elements that will have sorted arr
	output = [0] * (n)
	
	# initialize count array as 0
	count = [0] * (10)
	
	# Store count of occurrences in count[]
	for i in range(0, n):
		index = (arr[i]/exp1)
		count[int((index)%10)] += 1
	
	# Change count[i] so that count[i] now contains actual
	# position of this digit in output array
	for i in range(1,10):
		count[i] += count[i-1]
	
	# Build the output array
	i = n-1
	while i>=0:
		index = (arr[i]/exp1)
		output[ count[ int((index)%10) ] - 1] = arr[i]
		count[int((index)%10)] -= 1
		i -= 1
	
	# Copying the output array to arr[],
	# so that arr now contains sorted numbers
	i = 0
	for i in range(0,len(arr)):
		arr[i] = output[i]

# Method to do Radix Sort
def radixSort(arr):

	# Find the maximum number to know number of digits
	max1 = max(arr)

	# Do counting sort for every digit. Note that instead
	# of passing digit number, exp is passed. exp is 10^i
	# where i is current digit number
	exp = 1
	while max1/exp > 0:
		countingSort(arr,exp)
		exp *= 10

# Driver code to test above
arr = [ 170, 45, 75, 90, 802, 24, 2, 66]
radixSort(arr)

for i in range(len(arr)):
	print(arr[i]),

print("test")

def max_n(lst, n = 1):
  return sorted(lst, reverse = True)[:n]

max_n([1, 2, 3]) # [3]
max_n([1, 2, 3], 2) # [3, 2]

# Python program to reverse a linked list
# Time Complexity : O(n)
# Space Complexity : O(n) as 'next'
#variable is getting created in each loop.

# Node class


class Node:

	# Constructor to initialize the node object
	def __init__(self, data):
		self.data = data
		self.next = None


class LinkedList:

	# Function to initialize head
	def __init__(self):
		self.head = None

	# Function to reverse the linked list
	def reverse(self):
		prev = None
		current = self.head
		while(current is not None):
			next = current.next
			current.next = prev
			prev = current
			current = next
		self.head = prev

	# Function to insert a new node at the beginning
	def push(self, new_data):
		new_node = Node(new_data)
		new_node.next = self.head
		self.head = new_node

	# Utility function to print the linked LinkedList
	def printList(self):
		temp = self.head
		while(temp):
			print temp.data,
			temp = temp.next


# Driver program to test above functions
llist = LinkedList()
llist.push(20)
llist.push(4)
llist.push(15)
llist.push(85)

print "Given Linked List"
llist.printList()
llist.reverse()
print "\nReversed Linked List"
llist.printList()

primes=[]
products=[]

def prime(num):
    if num > 1:
        for i in range(2,num):
            if (num % i) == 0:
                return False
        else:
            primes.append(num)
            return True

for n in range(30,1000):
    if len(primes) >= 20:
        break;
    else:
        prime(n)

for previous, current in zip(primes[::2], primes[1::2]):
    products.append(previous * current)
    
print (products)