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29 lines
1.1 KiB
Go
29 lines
1.1 KiB
Go
package solver
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// A CardConstr is a cardinality constraint, i.e a set of literals (represented with integer variables) associated with a minimal number of literals that must be true.
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// A propositional clause (i.e a disjunction of literals) is a cardinality constraint with a minimal cardinality of 1.
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type CardConstr struct {
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Lits []int
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AtLeast int
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}
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// AtLeast1 returns a cardinality constraint stating that at least one of the given lits must be true.
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// This is the equivalent of a propositional clause.
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func AtLeast1(lits ...int) CardConstr {
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return CardConstr{Lits: lits, AtLeast: 1}
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}
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// AtMost1 returns a cardinality constraint stating that at most one of the given lits can be true.
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func AtMost1(lits ...int) CardConstr {
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negated := make([]int, len(lits))
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for i, lit := range lits {
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negated[i] = -lit
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}
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return CardConstr{Lits: negated, AtLeast: len(lits) - 1}
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}
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// Exactly1 returns two cardinality constraints stating that exactly one of the given lits must be true.
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func Exactly1(lits ...int) []CardConstr {
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return []CardConstr{AtLeast1(lits...), AtMost1(lits...)}
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}
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