1 files changed, 114 insertions, 0 deletions

diff --git a/2016/src/day02.cpp b/2016/src/day02.cpp
new file mode 100644
index 0000000..ad625d5
--- /dev/null
+++ b/2016/src/day02.cpp
@@ -0,0 +1,114 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <string>
+#include <tuple>
+#include <vector>
+
+using namespace std;
+
+vector<string>
+read_file(string_view filename)
+{
+        fstream        input{ filename };
+        vector<string> lines;
+
+        vector<tuple<char, long>> result;
+        for ( string line; getline(input, line); ) {
+                lines.emplace_back(line);
+        }
+        return lines;
+}
+
+void
+part1(const vector<string>& lines)
+{
+        int pos_x = 1;
+        int pos_y = 1;
+
+        for ( const auto& line: lines ) {
+                for ( const auto chr: line ) {
+                        switch ( chr ) {
+                        case 'U':
+                                --pos_y;
+                                break;
+                        case 'R':
+                                ++pos_x;
+                                break;
+                        case 'L':
+                                --pos_x;
+                                break;
+                        case 'D':
+                                ++pos_y;
+                                break;
+                        default:
+                                cerr << "unknown char: " << chr << endl;
+                                return;
+                        }
+
+                        pos_x = clamp(pos_x, 0, 2);
+                        pos_y = clamp(pos_y, 0, 2);
+                }
+                cout << pos_y * 3 + pos_x + 1;
+        }
+        cout << endl;
+}
+
+void
+part2(const vector<string>& lines)
+{
+        const map<tuple<int, int>, char> keypad = {
+                { { 2, 0 }, '1' },
+                { { 1, 1 }, '2' },
+                { { 2, 1 }, '3' },
+                { { 3, 1 }, '4' },
+                { { 0, 2 }, '5' },
+                { { 1, 2 }, '6' },
+                { { 2, 2 }, '7' },
+                { { 3, 2 }, '8' },
+                { { 4, 2 }, '9' },
+                { { 1, 3 }, 'A' },
+                { { 2, 3 }, 'B' },
+                { { 3, 3 }, 'C' },
+                { { 2, 4 }, 'D' }
+        };
+
+        tuple<int, int> pos = { 0, 2 };
+
+        for ( const auto& line: lines ) {
+                for ( const auto chr: line ) {
+                        auto pos2 = pos;
+                        switch ( chr ) {
+                        case 'U':
+                                --get<1>(pos2);
+                                break;
+                        case 'R':
+                                ++get<0>(pos2);
+                                break;
+                        case 'L':
+                                --get<0>(pos2);
+                                break;
+                        case 'D':
+                                ++get<1>(pos2);
+                                break;
+                        default:
+                                cerr << "unknown char: " << chr << endl;
+                                return;
+                        }
+
+                        if ( keypad.contains(pos2) ) {
+                                pos = pos2;
+                        }
+                }
+                cout << keypad.at(pos);
+        }
+        cout << endl;
+}
+
+int
+main()
+{
+        auto lines = read_file("data/day02.txt");
+        part1(lines);
+        part2(lines);
+}