interviewcake.com problem: Detect if a given single-rifle shuffled deck is possible from the given two halves.

output.txt

++ ./shuffle.py '[1]' '[2]' '[1,2]'
+ test True == True
++ ./shuffle.py '[1]' '[2]' '[2,1]'
+ test True == True
++ ./shuffle.py '[1,2]' '[3]' '[1,2,3]'
+ test True == True
++ ./shuffle.py '[1,2]' '[3]' '[1,3,2]'
+ test True == True
++ ./shuffle.py '[1,2]' '[3]' '[3,1,2]'
+ test True == True
++ ./shuffle.py '[1,2]' '[3]' '[2,1,3]'
+ test False == False
++ ./shuffle.py '[1,2]' '[3]' '[2,3,1]'
+ test False == False
++ ./shuffle.py '[1,2]' '[3]' '[3,2,1]'
+ test False == False
+ echo 'All tests passed.'
All tests passed.

shuffle.py

#!/usr/bin/env python

import sys
import json

def commonCount(list1, list2):
    if len(list1) == 0 or len(list2) == 0:
        return 0
    elif list1[:1] == list2[:1]:
        return 1 + commonCount(list1[1:], list2[1:])
    else:
        return 0

def isPossibleSingleRifleShuffle(half1, half2, shuffledDeck):
    if len(shuffledDeck) == 0:
        return True
    common1 = commonCount(half1, shuffledDeck)
    common2 = commonCount(half2, shuffledDeck)
    if common1:
        return True and isPossibleSingleRifleShuffle(half1[common1:], half2, shuffledDeck[common1:])
    elif common2:
        return True and isPossibleSingleRifleShuffle(half1, half2[common2:], shuffledDeck[common2:])
    else:
        return False

if len(sys.argv) < 4:
    sys.stderr.write("Error: bad arguments\n")
    sys.stderr.write("Usage: ./shuffle.py <half1 JSON> <half2 JSON> <shuffledDeck JSON>\n")
    sys.exit(1)

half1 = json.loads(sys.argv[1])
half2 = json.loads(sys.argv[2])
shuffledDeck = json.loads(sys.argv[3])

print isPossibleSingleRifleShuffle(half1, half2, shuffledDeck)

test.sh

#!/bin/bash

set -e -o pipefail
set -x

test "True" == `./shuffle.py [1] [2] [1,2]`
test "True" == `./shuffle.py [1] [2] [2,1]`

test "True" == `./shuffle.py [1,2] [3] [1,2,3]`
test "True" == `./shuffle.py [1,2] [3] [1,3,2]`
test "True" == `./shuffle.py [1,2] [3] [3,1,2]`
test "False" == `./shuffle.py [1,2] [3] [2,1,3]`
test "False" == `./shuffle.py [1,2] [3] [2,3,1]`
test "False" == `./shuffle.py [1,2] [3] [3,2,1]`

echo "All tests passed."