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Author Archives: possiblywrong
Generating MiniCrosswords
Introduction The New York Times publishes “minicrosswords,” which are crossword puzzles on a relatively small grid (usually 5×5), without any black squares, so that every row and column of the grid must spell a word. The figure below shows an … Continue reading
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Disabling subnormals in MATLAB
Suppose that we want to compute the following expression, somewhat contrived in complexity for the purpose of example: The following MATLAB code implements this formula, and measures the time required to evaluate it: Now suppose that we execute this same … Continue reading
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A lattice path puzzle
This past week’s Riddler puzzle on FiveThirtyEight asks for the number of different paths of minimum length from a starting intersection of city streets to a destination blocks east and blocks north. Put another way, moving on the 2D integer … Continue reading
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Arbitraryprecision rational arithmetic in C++
Introduction This is a followup to a post from several years ago describing a C++ implementation of arbitraryprecision unsigned integer arithmetic. This weekend I extended this to also support arbitraryprecision signed integers and rational numbers. Although this started as an educational … Continue reading
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Uncertainty in trading passengers for fuel
I had an interesting experience recently while preparing for a flight from Los Angeles to Baltimore. It was a completely full flight– initially, at least– with myself and 174 other passengers who had already boarded the Southwest 737800, seemingly ready … Continue reading
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An urn puzzle
It has been a while again since I last posted a puzzle, so… You have once again been captured by mathematicallyinclined pirates and threatened with walking the plank, unless you can win the following game: some number of black balls … Continue reading
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On average, we die a decade earlier than expected
“Doctors say he’s got a 50/50 chance of living… though there’s only a 10% chance of that.” I’ve lately had occasion to contemplate my own mortality. How long should I expect to live? The most recent life table published by the Centers … Continue reading
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