import copy import sys import random def cons(x, l): new_l = copy.copy(l) new_l.insert(0,x) return new_l def head (l): if l == []: print("Cannot call head on the empty list.", file=sys.stderr)...

# DO NOT CHANGE THE FOLLOWING CODE:
	import list_lib as ll
	# END SECTION OF CODE YOU'RE NOT CHANGING
	# Define an function called intersect that takes two arrays as input,
	# and then returns a new array that contains the elements which appear
	# in both of the input arrays. For example,
	#
	# intersect([1,2,42,5], [7,1,43,2,76,84]) = [1,2]
	# intersect([1,2,42,5], [42,43,76,5,1]) = [1,42,5]

import copy import sys import random def cons(x, l): new_l = copy.copy(l) new_l.insert(0,x) return new_l def head (l): if l == []: print("Cannot call head on the empty list.", file=sys.stderr) sys.exit() x , *xs = l return x def tail (l): if l == []: return [] x, *xs = l return xs def append(l1,l2): return l1 + l2 def reverse(l): new_l = copy.copy(l) new_l.reverse() return new_l def repeat(x,n): if n < 0:="" print="" ("cannot="" call="" repeat="" with="" negative="" values.",="" file="sys.stderr)" sys.exit()="" return="" [x]="" *="" n="" def="" _take(n,acc,l):="" if="" n="=" 0:="" return="" acc="" elif="" n="">< 0:="" print="" ("cannot="" call="" take="" with="" negagive="" values.",="" file="sys.stderr)" sys.exit()="" x="head(l)" rest="tail(l)" return="" _take="" (n-1,cons(x,acc),rest)="" def="" take(n,l):="" if="" l="=" []:="" return="" []="" return="" reverse="" (_take(n,[],l))="" def="" drop(n,l):="" if="" n="=" 0:="" return="" l="" elif="" n="">< 0:="" print="" ("cannot="" call="" drop="" with="" negative="" values.",="" file="sys.stderr)" sys.exit()="" es="tail" (l)="" return="" drop="" (n-1,="" es)="" def="" _length(acc,="" l):="" if="" l="=" []:="" return="" acc="" return="" _length(1+acc,tail(l))="" def="" length(l):="" return="" _length(0,l)="" def="" _randint_list(n,="" acc,="" low,="" high):="" if="" n="=" 0:="" return="" acc="" x="random.randint(low,high)" return="" _randint_list="" (n="" -="" 1,="" cons(x,acc),="" low,="" high)="" def="" randint_list(n,="" low,="" high):="" if="" n="">< 0:="" print="" ("cannot="" call="" randint_list="" with="" negative="" values.",="" file="sys.stderr)" sys.exit()="" return="" _randint_list(n,[],="" low,="" high)="" def="" _randfloat_list(n,="" acc,="" low,="" high):="" if="" n="=" 0:="" return="" acc="" x="random.randint(low,high)" return="" _randfloat_list="" (n="" -="" 1,="" cons(x,acc),="" low,="" high="" )="" def="" randfloat_list(n,="" low,="" high):="" if="" n="">< 0: print ("cannot call randint_list with negative values.", file=sys.stderr) sys.exit() return _randfloat_list(n,[], low, high) def unique(l): if l == []: return [] e = head (l) es = tail (l) new_tail = [x for x in es if x != e] return cons(e, unique(new_tail)) def list_range(low, high): return list(range(low, high)) 0:="" print="" ("cannot="" call="" randint_list="" with="" negative="" values.",="" file="sys.stderr)" sys.exit()="" return="" _randfloat_list(n,[],="" low,="" high)="" def="" unique(l):="" if="" l="=" []:="" return="" []="" e="head" (l)="" es="tail" (l)="" new_tail="[x" for="" x="" in="" es="" if="" x="" !="e]" return="" cons(e,="" unique(new_tail))="" def="" list_range(low,="" high):="" return="" list(range(low,="">