107 lines
3.5 KiB
C++
107 lines
3.5 KiB
C++
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/*******************************************************************************
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*
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* Copyright (c) 2020 Gnarwhal
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*
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* -----------------------------------------------------------------------------
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files(the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*******************************************************************************/
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#include <vector>
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#include <string>
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#include <iostream>
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#include <fstream>
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#include "../misc/types.hpp"
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#include "../misc/print.hpp"
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struct Pair{ u64 id; usize index; };
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auto find_least(u64 new_base, u64 new_loop, u64 req_base, u64 req_loop, u64 iter) -> u64 {
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while ((new_base + ++iter * new_loop - req_base) % req_loop != 0);
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return new_base + iter * new_loop;
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}
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auto day13() -> void {
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auto ready = usize(0);
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auto buses = std::vector<Pair>();
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{
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auto line = std::string();
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auto file = std::ifstream("inputs/day13.input");
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getline(file, line);
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ready = std::stoi(line);
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getline(file, line);
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auto start = usize(0);
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auto end = usize(0);
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auto index = usize(0);
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auto id = std::string();
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while ((end = line.find(',', start)) != std::string::npos) {
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id = line.substr(start, end - start);
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if (id != "x") {
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buses.push_back({ u64(std::stoi(line.substr(start, end - start))), index });
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}
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start = end + 1;
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++index;
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}
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end = line.size();
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id = line.substr(start, end - start);
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if (id != "x") {
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buses.push_back({ u64(std::stoi(line.substr(start, end - start))), index });
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}
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}
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auto id = buses[0].id;
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auto minutes = buses[0].id - (ready % buses[0].id);
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for (auto i = usize(1); i < buses.size(); ++i) {
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auto local_minutes = buses[i].id - (ready % buses[i].id);
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if (local_minutes < minutes) {
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id = buses[i].id;
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minutes = local_minutes;
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}
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}
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print((id * minutes));
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auto req_base = usize(0);
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auto req_loop = usize(1);
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for (auto i = usize(1); i < buses.size(); ++i) {
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auto base_loop = usize(-1);
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while ((++base_loop * buses[0].id + buses[i].index) % buses[i].id != 0);
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auto rep_loop = usize(0);
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while ((++rep_loop * buses[0].id) % buses[i].id != 0);
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req_base = find_least(base_loop, rep_loop, req_base, req_loop, -1);
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if (i < buses.size() - 1) {
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req_loop = find_least(0, rep_loop, 0, req_loop, 0);
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}
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/*
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required_base (rqb), required_loop (rql)
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base_loop (bl), repeat_loop (rl)
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rqb + a0 * rql = bl + a1 * rl < minimize and store in required loop
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a0 = (bl + a1 * rl - rqb) / rql
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b0 * rql = b1 * rl < minimize and store in required loop
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*/
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}
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print((req_base * buses[0].id));
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}
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