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  2. Langford pairing - Wikipedia

    en.wikipedia.org/wiki/Langford_pairing

    A Langford pairing for n = 4.. In combinatorial mathematics, a Langford pairing, also called a Langford sequence, is a permutation of the sequence of 2n numbers 1, 1, 2, 2, ..., n, n in which the two 1s are one unit apart, the two 2s are two units apart, and more generally the two copies of each number k are k units apart.

  3. Stable roommates problem - Wikipedia

    en.wikipedia.org/wiki/Stable_roommates_problem

    To find it, start at such a p 0 containing at least two individuals in their reduced list, and define recursively q i+1 to be the second on p i 's list and p i+1 to be the last on q i+1 's list, until this sequence repeats some p j, at which point a rotation is found: it is the sequence of pairs starting at the first occurrence of (p j, q j ...

  4. Stable marriage problem - Wikipedia

    en.wikipedia.org/wiki/Stable_marriage_problem

    In a uniformly-random instance of the stable marriage problem with n men and n women, the average number of stable matchings is asymptotically ⁡. [6] In a stable marriage instance chosen to maximize the number of different stable matchings, this number is an exponential function of n . [ 7 ]

  5. Fibonacci sequence - Wikipedia

    en.wikipedia.org/wiki/Fibonacci_sequence

    The number of binary strings of length n without an odd number of consecutive 1 s is the Fibonacci number F n+1. For example, out of the 16 binary strings of length 4, there are F 5 = 5 without an odd number of consecutive 1 s—they are 0000, 0011, 0110, 1100, 1111.

  6. Stars and bars (combinatorics) - Wikipedia

    en.wikipedia.org/wiki/Stars_and_bars_(combinatorics)

    For any pair of positive integers n and k, the number of k-tuples of positive integers whose sum is n is equal to the number of (k − 1)-element subsets of a set with n − 1 elements. For example, if n = 10 and k = 4, the theorem gives the number of solutions to x 1 + x 2 + x 3 + x 4 = 10 (with x 1, x 2, x 3, x 4 > 0) as the binomial coefficient

  7. Matroid parity problem - Wikipedia

    en.wikipedia.org/wiki/Matroid_parity_problem

    In it, a subset of edges is independent if its removal does not separate the graph. Any spanning tree of the original graph that avoids the edges used in the matroid parity solution is necessarily a Xuong tree. Each pair selected in the solution can be used to increase the genus of the embedding, so the total genus is the number of selected ...

  8. Partition problem - Wikipedia

    en.wikipedia.org/wiki/Partition_problem

    In number theory and computer science, the partition problem, or number partitioning, [1] is the task of deciding whether a given multiset S of positive integers can be partitioned into two subsets S 1 and S 2 such that the sum of the numbers in S 1 equals the sum of the numbers in S 2.

  9. Subset sum problem - Wikipedia

    en.wikipedia.org/wiki/Subset_sum_problem

    n - the number of input integers. If n is a small fixed number, then an exhaustive search for the solution is practical. L - the precision of the problem, stated as the number of binary place values that it takes to state the problem. If L is a small fixed number, then there are dynamic programming algorithms that can solve it exactly.