def _generate_solutions(cls, period, doms):
"""
Each child gets as domain a set of ShiftAssignables,
which is generated by their shift preferences;
each solution selects for each child a ShiftAssignable
so that all assignments are compatible.
Here we configure a problem from the constraint library,
then call the solver.
The problem takes a mapping, doms, from child_pk to a set of assignables for that child, plus a specification, across children, of which assignables are pairwise consistent
The solver yields all compatible sets of assignables
"""
problem = Problem()
prefs = (ShiftPreference.objects.filter(
period=period).select_related('shift').select_related('child'))
for pref in prefs:
for assignable in pref.assignables():
if assignable.is_active:
doms[assignable.child.pk].append(assignable)
for k, dom in doms.items():
try:
problem.addVariable(k, dom)
except ValueError:
return {}
cached_compatibility = functools.lru_cache()(
lambda a1, a2: a1.is_compatible_with(a2))
for k1, k2 in itertools.combinations(doms.keys(), 2):
problem.addConstraint(cached_compatibility, (k1, k2))
# call the solver
return problem.getSolutionIter()
def solve():
problem = Problem()
problem.addVariables("sendmory", range(10))
problem.addConstraint(lambda d, e, y: (d + e) % 10 == y, "dey")
problem.addConstraint(
lambda n, d, r, e, y: (n * 10 + d + r * 10 + e) % 100 == e * 10 + y, "ndrey"
)
problem.addConstraint(
lambda e, n, d, o, r, y: (e * 100 + n * 10 + d + o * 100 + r * 10 + e) % 1000 ==
n * 100 + e * 10 + y,
"endory",
)
problem.addConstraint(
lambda s, e, n, d, m, o, r, y: 1000 * s +
100 * e +
10 * n +
d +
1000 * m +
100 * o +
10 * r +
e ==
10000 * m + 1000 * o + 100 * n + 10 * e + y,
"sendmory",
)
problem.addConstraint(NotInSetConstraint([0]), "sm")
problem.addConstraint(AllDifferentConstraint())
solutions = problem.getSolutions()
return solutions
def find_mapping(signal_patterns: Set[FrozenSet[str]]) -> Dict[str, str]:
# Let’s express this as a constraint satisfaction problem
problem = Problem()
for signal in "abcdefg":
problem.addVariable(signal, "abcdefg")
# Each signal wire goes to a different segment
problem.addConstraint(AllDifferentConstraint())
# Unambiguous digits based on count of lit segments
for digit in {1, 4, 7, 8}:
for wire in find_possible_signals_for(signal_patterns, digit):
segments = DIGIT_TO_SEGMENTS[digit]
problem.addConstraint(InSetConstraint(segments), wire)
# Unambiguous segments based on how many times they appear in patterns
for signal_wire in {"a", "b", "c", "d", "e", "f", "g"}:
count = sum(1 for pattern in signal_patterns if signal_wire in pattern)
if count == 4:
problem.addConstraint(InSetConstraint(["e"]), signal_wire)
elif count == 6:
problem.addConstraint(InSetConstraint(["b"]), signal_wire)
elif count == 7:
problem.addConstraint(InSetConstraint(["d", "g"]), signal_wire)
elif count == 8:
problem.addConstraint(InSetConstraint(["a", "c"]), signal_wire)
elif count == 9:
problem.addConstraint(InSetConstraint(["f"]), signal_wire)
else:
raise ValueError
return problem.getSolution()
def solve():
problem = Problem()
# Define the variables: 9 rows of 9 variables rangin in 1...9
for i in range(1, 10):
problem.addVariables(range(i * 10 + 1, i * 10 + 10), range(1, 10))
# Each row has different values
for i in range(1, 10):
problem.addConstraint(AllDifferentConstraint(),
range(i * 10 + 1, i * 10 + 10))
# Each colum has different values
for i in range(1, 10):
problem.addConstraint(AllDifferentConstraint(),
range(10 + i, 100 + i, 10))
# Each 3x3 box has different values
problem.addConstraint(AllDifferentConstraint(),
[11, 12, 13, 21, 22, 23, 31, 32, 33])
problem.addConstraint(AllDifferentConstraint(),
[41, 42, 43, 51, 52, 53, 61, 62, 63])
problem.addConstraint(AllDifferentConstraint(),
[71, 72, 73, 81, 82, 83, 91, 92, 93])
problem.addConstraint(AllDifferentConstraint(),
[14, 15, 16, 24, 25, 26, 34, 35, 36])
problem.addConstraint(AllDifferentConstraint(),
[44, 45, 46, 54, 55, 56, 64, 65, 66])
problem.addConstraint(AllDifferentConstraint(),
[74, 75, 76, 84, 85, 86, 94, 95, 96])
problem.addConstraint(AllDifferentConstraint(),
[17, 18, 19, 27, 28, 29, 37, 38, 39])
problem.addConstraint(AllDifferentConstraint(),
[47, 48, 49, 57, 58, 59, 67, 68, 69])
problem.addConstraint(AllDifferentConstraint(),
[77, 78, 79, 87, 88, 89, 97, 98, 99])
# Some value is given.
initValue = [[0, 9, 0, 7, 0, 0, 8, 6, 0], [0, 3, 1, 0, 0, 5, 0, 2, 0],
[8, 0, 6, 0, 0, 0, 0, 0, 0], [0, 0, 7, 0, 5, 0, 0, 0, 6],
[0, 0, 0, 3, 0, 7, 0, 0, 0], [5, 0, 0, 0, 1, 0, 7, 0, 0],
[0, 0, 0, 0, 0, 0, 1, 0, 9], [0, 2, 0, 6, 0, 0, 0, 5, 0],
[0, 5, 4, 0, 0, 8, 0, 7, 0]]
for i in range(1, 10):
for j in range(1, 10):
if initValue[i - 1][j - 1] != 0:
problem.addConstraint(
lambda var, val=initValue[i - 1][j - 1]: var == val,
(i * 10 + j, ))
# Get the solutions.
solutions = problem.getSolutions()
return solutions
