The challenge
Implement the function unique_in_order which takes as argument a sequence and returns a list of items without any elements with the same value next to each other and preserving the original order of elements.
For example:
unique_in_order('AAAABBBCCDAABBB') == ['A', 'B', 'C', 'D', 'A', 'B']
unique_in_order('ABBCcAD') == ['A', 'B', 'C', 'c', 'A', 'D']
unique_in_order([1,2,2,3,3]) == [1,2,3]
The solution in Python code
Option 1:
def unique_in_order(iterable):
result = []
prev = None
for char in iterable[0:]:
if char != prev:
result.append(char)
prev = char
return result
Option 2:
def unique_in_order(iterable):
r = []
for x in iterable:
x in r[-1:] or r.append(x)
return r
Option 3:
from itertools import groupby
def unique_in_order(iterable):
return [x for (x, _) in groupby(iterable)]
Test cases to validate our solution
test.describe("lets test it")
test.it("should work with empty array")
test.assert_equals(unique_in_order(''),[])
test.it("should work with one element")
test.assert_equals(unique_in_order('A'),['A'])
test.it("should reduce duplicates")
test.assert_equals(unique_in_order('AA'),['A'])
test.assert_equals(unique_in_order('AAAABBBCCDAABBB'),['A', 'B', 'C', 'D', 'A', 'B'])
test.assert_equals(unique_in_order('AADD'),['A','D'])
test.assert_equals(unique_in_order('AAD'),['A','D'])
test.assert_equals(unique_in_order('ADD'),['A','D'])
test.it("and treat lowercase as different from uppercase")
test.assert_equals(unique_in_order('ABBCcAD'),['A', 'B', 'C', 'c', 'A', 'D'])
test.it("and work with int arrays")
test.assert_equals(unique_in_order([1,2,3,3]),[1,2,3])
test.it("and work with char arrays")
test.assert_equals(unique_in_order(['a','b','b']),['a','b'])
