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Add 2016 day 21 puzzles

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This commit is contained in:
Matthew Gretton-Dann
2021-12-07 19:45:38 +00:00
parent d3622ff806
commit 6448f4c487
2 changed files with 213 additions and 0 deletions
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100
2016/puzzle-21-01.cc Normal file
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#include <iostream>
#include <regex>
#include <string>
auto swap_pos(std::string s, std::size_t a, std::size_t b) -> std::string
{
std::swap(s.at(a), s.at(b));
return s;
}
auto swap_letters(std::string const& s, char a, char b) -> std::string
{
std::string result;
std::transform(s.begin(), s.end(), std::back_inserter(result), [a, b](char c) {
if (c == a) {
return b;
}
if (c == b) {
return a;
}
return c;
});
return result;
}
auto rotate_left(std::string const& s, std::size_t amt) -> std::string
{
amt %= s.size();
return (s + s).substr(amt, s.size());
}
auto rotate_right(std::string const& s, std::size_t amt) -> std::string
{
amt %= s.size();
return (s + s).substr(s.size() - amt, s.size());
}
auto rotate_on_index(std::string const& s, char c) -> std::string
{
auto idx{s.find(c)};
std::size_t amt{1 + idx + (idx >= 4 ? 1 : 0)};
return rotate_right(s, amt);
}
auto reverse_str(std::string s, std::size_t a, std::size_t b) -> std::string
{
std::reverse(s.begin() + a, s.begin() + b + 1);
return s;
}
auto move(std::string s, std::size_t a, std::size_t b) -> std::string
{
auto c{s.at(a)};
s.erase(a, 1);
s.insert(s.begin() + b, c);
return s;
}
auto main() -> int
{
static std::regex swap_pos_re{"swap position (\\d+) with position (\\d+)"};
static std::regex swap_letter_re{"swap letter (.) with letter (.)"};
static std::regex rotate_left_re{"rotate left (\\d+) steps?"};
static std::regex rotate_right_re{"rotate right (\\d+) steps?"};
static std::regex rotate_based_re{"rotate based on position of letter (.)"};
static std::regex reverse_re{"reverse positions (\\d+) through (\\d+)"};
static std::regex move_re{"move position (\\d+) to position (\\d+)"};
std::string password{"abcdefgh"};
std::string line;
std::smatch m;
while (std::getline(std::cin, line)) {
if (std::regex_search(line, m, swap_pos_re)) {
password = swap_pos(password, std::stoul(m.str(1)), std::stoul(m.str(2)));
}
else if (std::regex_search(line, m, swap_letter_re)) {
password = swap_letters(password, m.str(1)[0], m.str(2)[0]);
}
else if (std::regex_search(line, m, rotate_left_re)) {
password = rotate_left(password, std::stoul(m.str(1)));
}
else if (std::regex_search(line, m, rotate_right_re)) {
password = rotate_right(password, std::stoul(m.str(1)));
}
else if (std::regex_search(line, m, rotate_based_re)) {
password = rotate_on_index(password, m.str(1)[0]);
}
else if (std::regex_search(line, m, reverse_re)) {
password = reverse_str(password, std::stoul(m.str(1)), std::stoul(m.str(2)));
}
else if (std::regex_search(line, m, move_re)) {
password = move(password, std::stoul(m.str(1)), std::stoul(m.str(2)));
}
else {
std::cerr << "Unable to interpret " << line << "\n";
return 1;
}
std::cout << line << " -> " << password << '\n';
}
std::cout << password << '\n';
}

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2016/puzzle-21-02.cc Normal file
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#include <iostream>
#include <regex>
#include <string>
auto swap_pos(std::string s, std::size_t a, std::size_t b) -> std::string
{
std::swap(s.at(a), s.at(b));
return s;
}
auto swap_letters(std::string const& s, char a, char b) -> std::string
{
std::string result;
std::transform(s.begin(), s.end(), std::back_inserter(result), [a, b](char c) {
if (c == a) {
return b;
}
if (c == b) {
return a;
}
return c;
});
return result;
}
auto rotate_left(std::string const& s, std::size_t amt) -> std::string
{
amt %= s.size();
return (s + s).substr(amt, s.size());
}
auto rotate_right(std::string const& s, std::size_t amt) -> std::string
{
amt %= s.size();
return (s + s).substr(s.size() - amt, s.size());
}
auto rotate_on_index(std::string const& s, char c) -> std::string
{
auto idx{s.find(c)};
std::size_t amt{1 + idx + (idx >= 4 ? 1 : 0)};
return rotate_right(s, amt);
}
auto reverse_str(std::string s, std::size_t a, std::size_t b) -> std::string
{
std::reverse(s.begin() + a, s.begin() + b + 1);
return s;
}
auto move(std::string s, std::size_t a, std::size_t b) -> std::string
{
auto c{s.at(a)};
s.erase(a, 1);
s.insert(s.begin() + b, c);
return s;
}
auto main() -> int
{
static std::regex swap_pos_re{"swap position (\\d+) with position (\\d+)"};
static std::regex swap_letter_re{"swap letter (.) with letter (.)"};
static std::regex rotate_left_re{"rotate left (\\d+) steps?"};
static std::regex rotate_right_re{"rotate right (\\d+) steps?"};
static std::regex rotate_based_re{"rotate based on position of letter (.)"};
static std::regex reverse_re{"reverse positions (\\d+) through (\\d+)"};
static std::regex move_re{"move position (\\d+) to position (\\d+)"};
std::string password{"fbgdceah"};
std::string line;
std::smatch m;
std::vector<std::string> commands;
while (std::getline(std::cin, line)) {
commands.push_back(line);
}
for (auto cmd{commands.rbegin()}; cmd != commands.rend(); ++cmd) {
if (std::regex_search(*cmd, m, swap_pos_re)) {
password = swap_pos(password, std::stoul(m.str(1)), std::stoul(m.str(2)));
}
else if (std::regex_search(*cmd, m, swap_letter_re)) {
password = swap_letters(password, m.str(1)[0], m.str(2)[0]);
}
else if (std::regex_search(*cmd, m, rotate_left_re)) {
password = rotate_right(password, std::stoul(m.str(1)));
}
else if (std::regex_search(*cmd, m, rotate_right_re)) {
password = rotate_left(password, std::stoul(m.str(1)));
}
else if (std::regex_search(*cmd, m, rotate_based_re)) {
/* This is the only reverse command whose inverse is not obvious to me. So just do repeated
* rotations until we get to one which works.
*/
std::string trial{password};
while (rotate_on_index(trial, m.str(1)[0]) != password) {
trial = rotate_left(trial, 1);
};
password = trial;
}
else if (std::regex_search(*cmd, m, reverse_re)) {
password = reverse_str(password, std::stoul(m.str(1)), std::stoul(m.str(2)));
}
else if (std::regex_search(*cmd, m, move_re)) {
password = move(password, std::stoul(m.str(2)), std::stoul(m.str(1)));
}
else {
std::cerr << "Unable to interpret " << *cmd << "\n";
return 1;
}
std::cout << *cmd << " -> " << password << '\n';
}
std::cout << password << '\n';
}