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@boyter boyter/puzzle.py
Last active Apr 9, 2017

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Friday Quiz Solution
# Three people are playing the following betting game.
# Every five minutes, a turn takes place in which a random player rests and the other two bet
# against one another with all of their money.
# The player with the smaller amount of money always wins,
# doubling his money by taking it from the loser.
# For example, if the initial amounts of money are 1, 4, and 6,
# then the result of the first turn can be either
# 2,3,6 (1 wins against 4);
# 1,8,2 (4 wins against 6); or
# 2,4,5 (1 wins against 6).
# If two players with the same amount of money play against one another,
# the game immediately ends for all three players.
# Find initial amounts of money for the three players, where none of the three has more than 255,
# and in such a way that the game cannot end in less than one hour. (So at least 12 turns)
# In the example above (1,4,6), there is no way to end the game in less than 15 minutes.
# All numbers must be positive integers.
DESIRED_TURNS = 11
MAX_MONEY = 256
# Calculate all the possible sequences for who misses out for each turn
def calc_events(current=[], turn=0):
if turn == DESIRED_TURNS:
return [current]
one = list(current)
one.append(0)
two = list(current)
two.append(1)
three = list(current)
three.append(2)
turn += 1
path1 = calc_events(current=one, turn=turn)
path2 = calc_events(current=two, turn=turn)
path3 = calc_events(current=three, turn=turn)
return path1 + path2 + path3
def play_games(p1, p2, p3, events):
for event in events:
c1 = p1
c2 = p2
c3 = p3
for x in event:
if x == 0:
if c2 == c3:
return [False, p1, p2, p3]
if c2 > c3:
c2 = c2 - c3
c3 = c3 + c3
else:
c3 = c3 - c2
c2 = c2 + c2
if x == 1:
if c1 == c3:
return [False, p1, p2, p3]
if c1 > c3:
c1 = c1 - c3
c3 = c3 + c3
else:
c3 = c3 - c1
c1 = c1 + c1
if x == 2:
if c1 == c2:
return [False, p1, p2, p3]
if c1 > c2:
c1 = c1 - c2
c2 = c2 + c2
else:
c2 = c2 - c1
c1 = c1 + c1
return [True, p1, p2, p3]
if __name__ == '__main__':
possible_events = calc_events()
combinations = []
for x in xrange(1, MAX_MONEY):
for y in xrange(x, MAX_MONEY):
for z in [b for b in xrange(y, MAX_MONEY) if b != x and b != y]:
combinations.append([x, y, z])
results = [play_games(x[0], x[1], x[2], possible_events) for x in combinations]
print [x for x in results if x[0]]
@boyter

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Owner Author

commented Mar 27, 2017

Using PyPy

[[175, 199, 223], [197, 205, 213], [209, 217, 225]]

real	10m2.554s
user	9m13.108s
sys	0m7.010s
@boyter

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Owner Author

commented Mar 28, 2017

Made more pythonic and improved performance to boot

[[True, 175, 199, 223], [True, 197, 205, 213], [True, 209, 217, 225]]

real	7m42.951s
user	7m36.011s
sys	0m1.465s
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