[Merged by Bors] - feat(combinatorics/double_counting): Double-counting the edges of a bipartite graph #11372
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…ipartite graph (#11372) This proves a classic of double-counting arguments: If each element of the `|α|` elements on the left is connected to at least `m` elements on the right and each of the `|β|` elements on the right is connected to at most `n` elements on the left, then `|α| * m ≤ |β| * n` because the LHS is less than the number of edges which is less than the RHS. This is put in a new file `combinatorics.double_counting` with the idea that we could gather double counting arguments here, much as is done with `combinatorics.pigeonhole`.
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…ipartite graph (#11372) This proves a classic of double-counting arguments: If each element of the `|α|` elements on the left is connected to at least `m` elements on the right and each of the `|β|` elements on the right is connected to at most `n` elements on the left, then `|α| * m ≤ |β| * n` because the LHS is less than the number of edges which is less than the RHS. This is put in a new file `combinatorics.double_counting` with the idea that we could gather double counting arguments here, much as is done with `combinatorics.pigeonhole`.
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This proves a classic of double-counting arguments: If each element of the
|α|elements on the left is connected to at leastmelements on the right and each of the|β|elements on the right is connected to at mostnelements on the left, then|α| * m ≤ |β| * nbecause the LHS is less than the number of edges which is less than the RHS.This is put in a new file
combinatorics.double_countingwith the idea that we could gather double counting arguments here, much as is done withcombinatorics.pigeonhole.