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「充足可能性問題(3-SAT)を解く乱択アルゴリズム」 by Julia ref: http://qiita.com/antimon2/items/96e3bd6e452e03cf98db
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# Rw3sat.jl | |
sample(a::Array) = a[rand(1:end)] | |
immutable Literal | |
index::Int | |
not::Bool | |
end | |
literal(index, not) = Literal(index, not) | |
# issatisfied(l::Literal, x::BitArray{1}) = l.not ? !x[l.index] : x[l.index] | |
issatisfied(l::Literal, x::BitArray{1}) = l.not $ x[l.index] | |
immutable Clause | |
literals::Array{Literal, 1} | |
end | |
clause(ls::Literal...) = Clause([ls...]) | |
issatisfied(c::Clause, x::BitArray{1}) = any(l -> issatisfied(l, x), c.literals) | |
immutable CNF | |
clauses::Array{Clause, 1} | |
end | |
cnf(cs::Clause...) = CNF([cs...]) | |
issatisfied(f::CNF, x::BitArray{1}) = all(c -> issatisfied(c, x), f.clauses) | |
function rw3sat(f::CNF, n::Int, rr::Int) | |
for r = 1:rr | |
x = randbool(n) # W4 | |
for k = 1:3n | |
if issatisfied(f, x) # W7 | |
return "充足可能である" | |
end | |
c = sample(filter(c -> !issatisfied(c, x), f.clauses)) # W10 | |
idx = sample(c.literals).index # W11 | |
x[idx] = !x[idx] # W12 | |
end | |
end | |
return "おそらく充足不可能である" | |
end | |
p1 = clause(literal(1, false), literal(2, false), literal(3, false)) | |
p2 = clause(literal(4, false), literal(2, false), literal(3, true )) | |
p3 = clause(literal(1, true ), literal(4, false), literal(3, false)) | |
p4 = clause(literal(1, true ), literal(4, true ), literal(2, false)) | |
p5 = clause(literal(4, true ), literal(2, true ), literal(3, false)) | |
p6 = clause(literal(1, true ), literal(2, true ), literal(3, true )) | |
p7 = clause(literal(1, false), literal(4, true ), literal(3, true )) | |
p8 = clause(literal(1, false), literal(4, false), literal(2, true )) | |
f = cnf(p1, p2, p3, p4, p5, p6, p7, p8) | |
# f = cnf(p1, p2, p3, p4, p5, p6, p8) | |
println(rw3sat(f, 4, 3)) | |
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