Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Collatz Conjecture (Python Example)
#!/usr/bin/python
#
# Collatz Conjecture:
# x → x/2 (if x is even)
# x → 3x + 1 (if x is odd)
import sys, time
# Default seed if no arguments given
seed = 27
def collatz_sequence(x):
seq = [x]
while seq[-1] > 1:
if x % 2 == 0:
seq.append(int(x/2))
else:
seq.append(int(3*x+1))
x = seq[-1]
return seq
# test for cli arguments
try:
if len(sys.argv)>1 :
seed = int(sys.argv[1])
except ValueError:
print("Not a number.")
sys.exit(1)
# time the method
start = time.time()
# execute function
list = collatz_sequence(seed)
# stop/record our stopwatch
finish = (time.time() - start)
# print list and total list items
print("\nSeed = " + str(seed) + "\n")
print(list)
print("\nItems = " + str(len(list)))
# time spent
print("\nFunction took {} milliseconds".format(1000 * finish))
#print("Script execution took {} milliseconds\n".format(1000 * (time.time() - start)))
# clean exit
print()
sys.exit(0)
# Collatz Conjecture:
# x → x/2 (if x is even)
# x → 3x + 1 (if x is odd)
#
# Calculate max amount of elements in numbers 1-(iterations):
import sys, time, operator
# Range to cover 1 - (iteratons - 1)
iterations = 1000001
def collatz_sequence(x):
seq = [x]
while seq[-1] > 1:
if x % 2 == 0:
seq.append(int(x/2))
else:
seq.append(int(3*x+1))
x = seq[-1]
return seq
start = time.time()
# set our dictionary and for loop
Fullcount = {}
for number in range(1, iterations):
list = collatz_sequence(number)
Fullcount[number] = len(list)
# print("Seed = " + str(number) + " , " + "Items = " + str(len(list)))
# stop/record our stopwatch
finish = (time.time() - start)
# alternative way to find max key
#max(Fullcount.keys(), key=(lambda k: Fullcount[k]))
# find max key
maximum = max(Fullcount, key=Fullcount.get)
print()
print("Range to test: 1 - " + str(iterations - 1) + "\n" + "The number " + str(maximum) + " wins.\nIt has " + str(Fullcount[maximum]) + " items.")
# time spent
print("\nFunction took {} milliseconds".format(1000 * finish))
# clean exit
print()
sys.exit(0)
@bmatthewshea
Copy link
Author

Default is 27 / no line arguments.

SHEA22-2021-08-17_101032

@bmatthewshea
Copy link
Author

bmatthewshea commented Aug 17, 2021

Find max in range (Example 2 / second script) then you can show elements by running first script on same number found:

SHEA22-2021-08-17_133847

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment