stars and bars method

E141902

The stars and bars method is a classic combinatorial technique used to count the number of ways to distribute indistinguishable objects into distinct bins, often applied to problems involving nonnegative integer solutions to equations.

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balls and urns method 1
stars and bars method canonical 1

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Predicate Object
instanceOf combinatorial method
counting technique
problem-solving technique
appearsIn discrete mathematics courses
introductory combinatorics textbooks
probability courses
appliedIn counting integer solutions under simple constraints
counting polynomial solutions with nonnegative integer exponents
distribution of identical prizes among people
occupancy problems
assumes bins are distinguishable
objects are indistinguishable
order of objects within a bin does not matter
basedOn bijection between distributions and bar placements
combinatorial reasoning
canBeAdaptedTo positive integer solutions via variable shifts
canBeGeneralizedTo some bounded integer solution problems
contrastsWith permutation counting of distinguishable objects
field combinatorics
hasAlternativeName balls and bars method
stars and bars method
surface form: balls and urns method

bars and stars method
historicalContext classical technique in 19th–20th century combinatorics
involves choosing bar positions among stars and bars
mapping distributions to binary strings of stars and bars
representing objects as stars
representing separators as bars
prerequisite basic combinatorial reasoning
basic understanding of binomial coefficients
relatedTo binomial coefficients
combinations with repetition
integer partitions with restricted parts
multinomial coefficients
multiset combinations
weak compositions
requires nonnegative integer variables in its standard form
taughtAtLevel advanced high school mathematics
undergraduate mathematics
typicalFormula C(n + k - 1, k - 1) for nonnegative solutions of x1 + ... + xk = n
C(n - 1, k - 1) for positive solutions of x1 + ... + xk = n
usedFor counting distributions of indistinguishable objects into distinct bins
counting nonnegative integer solutions of linear equations
counting solutions to x1 + x2 + ... + xk = n with xi > 0
counting solutions to x1 + x2 + ... + xk = n with xi ≥ 0
counting weak compositions of an integer
distributing identical balls into labeled boxes
problems in discrete probability
problems in enumerative combinatorics

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Full triples — surface form annotated when it differs from this entity's canonical label.

multinomial theorem connectedTo stars and bars method
stars and bars method hasAlternativeName stars and bars method
this entity surface form: balls and urns method