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  2. 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

  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. 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.

  5. Stable marriage problem - Wikipedia

    en.wikipedia.org/wiki/Stable_marriage_problem

    In 1962, David Gale and Lloyd Shapley proved that, for any equal number of men and women, it is always possible to solve the stable marriage problem and make all marriages stable. They presented an algorithm to do so. [9] [10] The Gale–Shapley algorithm (also known as the deferred acceptance algorithm) involves a number of "rounds" (or ...

  6. LeetCode - Wikipedia

    en.wikipedia.org/wiki/LeetCode

    LeetCode LLC, doing business as LeetCode, is an online platform for coding interview preparation. The platform provides coding and algorithmic problems intended for users to practice coding . [ 1 ] LeetCode has gained popularity among job seekers in the software industry and coding enthusiasts as a resource for technical interviews and coding ...

  7. Mathematics of Sudoku - Wikipedia

    en.wikipedia.org/wiki/Mathematics_of_Sudoku

    Initial analysis was largely focused on enumerating solutions, with results first appearing in 2004. [1] For classical Sudoku, the number of filled grids is 6,670,903,752,021,072,936,960 (6.671 × 10 21), which reduces to 5,472,730,538 essentially different solutions under the validity-preserving

  8. 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.

  9. Steinhaus–Johnson–Trotter algorithm - Wikipedia

    en.wikipedia.org/wiki/Steinhaus–Johnson...

    The ! permutations of the numbers from 1 to may be placed in one-to-one correspondence with the ! numbers from 0 to ! by pairing each permutation with the sequence of numbers that count the number of positions in the permutation that are to the right of value and that contain a value less than (that is, the number of inversions for which is the ...