Find combinations of integers from 3 lists that sum to the items in a target list

combosums.py

#!/usr/bin/env python3

''' Find combinations of integers from 3 lists that sum to the items in a target list

    https://gist.github.com/PM2Ring/f051ab09f9074ab5a378fa30f4141352

    Written by PM 2Ring 2017.10.15
'''

from itertools import product
from random import seed, sample

seed(42)

# The highest number in the target list
target_high = 18
# Source lists size
size = 6

# The highest number in the source lists
source_high = 10

# Make the target set
target_range = range(1, target_high + 1)
targets = set(target_range)

# Make three random source lists of unique numbers
sources = []
source_range = range(1, source_high + 1)
sources = [sorted(sample(source_range, size)) for _ in range(3)]
sources.sort()
print('Source lists:', *sources, sep='\n', end='\n\n')

# Use the first 2 sources lists to make sums and then pair those sums 
# with the numbers in the last sources list to search for target numbers
last = sources[-1]

found = {}
for a, b in product(*sources[:2]):
    s = a + b
    hi = max(targets)
    if s > hi:
        continue
    # Combine this pair with each item in last
    for c in last:
        t = s + c
        if t > hi:
            break
        if t in targets:
            targets.remove(t)
            row = (a, b, c)
            found[t] = row
            #print(row, t)

for t in target_range:
    if t in found:
        print(t, found[t])