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108 lines
2.2 KiB
108 lines
2.2 KiB
#include <iostream>
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#include <vector>
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#include <unordered_set>
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using namespace std;
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enum Dir {
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UP,
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DOWN,
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RIGHT,
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LEFT
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};
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struct Instr {
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enum Dir dir;
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unsigned steps;
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};
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struct Pos2d {
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int x, y;
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Pos2d operator+(const Pos2d &r) const
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{
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return {this->x + r.x, this->y + r.y};
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}
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void operator+=(const Pos2d &r) { *this = *this + r; }
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Pos2d operator-(const Pos2d &r) const
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{
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return {this->x - r.x, this->y - r.y};
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}
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bool operator==(const Pos2d &r) const
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{
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return this->x == r.x && this->y == r.y;
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}
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};
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Pos2d dirs[] = {
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{0, 1},
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{0, -1},
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{1, 0},
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{-1, 0}
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};
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typedef vector<Instr> Input;
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template<>
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struct std::hash<Pos2d> {
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size_t operator()(const Pos2d &r) const
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{
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return hash<int>{}(r.x) ^ (hash<int>{}(r.y) << 1);
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}
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};
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Input parse()
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{
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Input data;
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for (string line; getline(cin, line);) {
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Instr instr;
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if (line.size() < 3 || line.at(1) != ' ') throw "parse";
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switch (line.at(0)) {
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case 'U': instr.dir = UP; break;
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case 'D': instr.dir = DOWN; break;
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case 'L': instr.dir = LEFT; break;
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case 'R': instr.dir = RIGHT; break;
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}
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instr.steps = stoi(line.substr(2));
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data.push_back(instr);
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}
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return data;
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}
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unsigned p1(const Input &input, unsigned count = 2)
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{
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auto knot = vector<Pos2d>(count);
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unordered_set<Pos2d> visited;
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visited.insert(knot.back());
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for (auto x : input) {
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for (unsigned i = 0; i < x.steps; i++) {
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knot.front() += dirs[x.dir];
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for (auto el = knot.begin(); el < knot.end() - 1; el++) {
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Pos2d dist = el[0] - el[1];
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if (abs(dist.x) >= 2 || abs(dist.y) >= 2) {
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if (abs(dist.x) >= 2) dist.x = dist.x > 0 ? 1 : -1;
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if (abs(dist.y) >= 2) dist.y = dist.y > 0 ? 1 : -1;
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el[1] += dist;
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continue;
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}
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break;
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}
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visited.insert(knot.back());
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}
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}
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return visited.size();
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}
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unsigned p2(const Input &input)
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{
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return p1(input, 10);
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}
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int main()
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{
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auto input = parse();
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cout << p1(input) << endl;
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cout << p2(input) << endl;
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}
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