78 lines
2.0 KiB
C++
78 lines
2.0 KiB
C++
#include <iostream>
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#include <iomanip>
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#include <cmath> // for log10()
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#include <algorithm> // for max()
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size_t table_column_width(const int min, const int max)
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{
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unsigned int abs_max = std::max(max*max, min*min);
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// abs_max is the largest absolute value we might see.
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// If we take the log10 and add one, we get the string width
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// of the largest possible absolute value.
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// Add one more for a little whitespace guarantee.
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size_t colwidth = 2 + std::log10(abs_max);
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// If only one of them is less than 0, then some will
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// be negative. If some values may be negative, then we need to add some space
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// for a sign indicator (-)
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if (min < 0 && max > 0)
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++colwidth;
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return colwidth;
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}
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struct Writer_
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{
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decltype(std::setw(1)) fmt_;
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Writer_(size_t w) : fmt_(std::setw(w)) {}
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template<class T_> Writer_& operator()(const T_& info) { std::cout << fmt_ << info; return *this; }
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};
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void print_table_header(const int min, const int max)
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{
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Writer_ write(table_column_width(min, max));
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// table corner
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write(" ");
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for(int col = min; col <= max; ++col)
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write(col);
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// End header with a newline and blank line.
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std::cout << std::endl << std::endl;
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}
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void print_table_row(const int num, const int min, const int max)
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{
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Writer_ write(table_column_width(min, max));
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// Header column
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write(num);
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// Spacing to ensure only the top half is printed
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for(int multiplicand = min; multiplicand < num; ++multiplicand)
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write(" ");
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// Remaining multiplicands for the row.
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for(int multiplicand = num; multiplicand <= max; ++multiplicand)
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write(num * multiplicand);
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// End row with a newline and blank line.
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std::cout << std::endl << std::endl;
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}
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void print_table(const int min, const int max)
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{
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// Header row
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print_table_header(min, max);
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// Table body
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for(int row = min; row <= max; ++row)
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print_table_row(row, min, max);
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}
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int main()
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{
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print_table(1, 12);
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return 0;
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}
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