60 lines
1.5 KiB
C++
60 lines
1.5 KiB
C++
#include <cassert>
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#include <iostream>
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#include <string>
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/** \brief Return the position described by BSP in s.
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* \tparam L2 log2 of the max position.
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* \tparam LOWER character which means use lower half.
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* \tparam UPPER character which means use upper half.
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* \param s String to parse, must be L2 characters long
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* \return Position described by s.
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*/
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template <unsigned L2, char LOWER, char UPPER>
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unsigned find_pos(std::string const &s) {
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assert(s.length() == L2);
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unsigned low = 0;
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unsigned high = 1 << L2;
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unsigned width = 1 << (L2 - 1);
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for (auto c : s) {
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assert(high != low);
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assert(width != 0);
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if (c == LOWER) {
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high = low + width;
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} else if (c == UPPER) {
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low = low + width;
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} else {
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assert(false);
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}
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width >>= 1;
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}
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assert(low == high - 1);
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return low;
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}
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template <unsigned L2R, unsigned L2C> struct Seat {
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Seat(std::string const &s) {
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assert(s.length() == L2R + L2C);
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row_ = find_pos<L2R, 'F', 'B'>(s.substr(0, L2R));
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col_ = find_pos<L2C, 'L', 'R'>(s.substr(L2R, L2C));
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std::cout << s << ": row " << row_ << ", column " << col_ << ", seat ID "
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<< id() << ".\n";
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}
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unsigned id() const noexcept { return row_ * (1 << L2C) + col_; }
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unsigned row_;
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unsigned col_;
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};
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int main(int argc, char **argv) {
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unsigned max_id = 0;
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for (std::string line; std::getline(std::cin, line);) {
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Seat<7, 3> seat(line);
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max_id = std::max(max_id, seat.id());
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}
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std::cout << "Max ID: " << max_id << "\n";
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return 0;
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} |