1 files changed, 145 insertions, 0 deletions

diff --git a/src/day11.cpp b/src/day11.cpp
new file mode 100644
index 0000000..baa1d9e
--- /dev/null
+++ b/src/day11.cpp
@@ -0,0 +1,145 @@
+#include <cmath>
+#include <fstream>
+#include <iostream>
+#include <set>
+#include <string>
+#include <vector>
+using namespace std;
+
+vector<string>
+read_file(string_view filename)
+{
+        fstream        input{ filename };
+        vector<string> data;
+
+        for ( string line; getline(input, line); ) {
+                data.emplace_back(line);
+        }
+
+        return data;
+}
+
+vector<string>
+expand(const vector<string>& input)
+{
+        vector<string> result;
+
+        for ( const auto& line: input ) {
+                if ( line.find('#') == line.npos ) {
+                        result.emplace_back(line);
+                }
+                result.emplace_back(line);
+        }
+
+        for ( size_t col = 0; col != result[0].size(); ++col ) {
+                bool empty_col = true;
+                for ( const auto& line: result ) {
+                        if ( line[col] == '#' ) {
+                                empty_col = false;
+                        }
+                }
+                if ( empty_col ) {
+                        for ( auto& line: result ) {
+                                line.insert(col, 1, '.');
+                        }
+                        ++col;
+                }
+        }
+
+        return result;
+}
+
+vector<tuple<long, long>>
+find_points(const vector<string>& input)
+{
+        vector<tuple<long, long>> result;
+
+        for ( size_t row = 0; row != input.size(); ++row ) {
+                const auto& line = input[row];
+
+                for ( size_t col = 0; col != line.size(); ++col ) {
+                        if ( line[col] == '#' ) {
+                                result.emplace_back(long(row), long(col));
+                        }
+                }
+        }
+
+        return result;
+}
+
+void
+solve(const vector<tuple<long, long>>& points)
+{
+        long sum = 0;
+        for ( size_t i = 0; i != points.size(); ++i ) {
+                for ( size_t j = i + 1; j != points.size(); ++j ) {
+                        const auto& from = points[i];
+                        const auto& to   = points[j];
+
+                        sum += abs(get<0>(from) - get<0>(to)) + abs(get<1>(from) - get<1>(to));
+                }
+        }
+        cout << sum << endl;
+
+}
+
+void
+part1()
+{
+        solve(find_points(expand(read_file("data/day11.txt"))));
+}
+
+void
+find_empty_rows_ans_cols(const vector<string>& input, set<long>& cols, set<long>& rows)
+{
+        cols.clear();
+        rows.clear();
+
+        for ( size_t row = 0; row != input.size(); ++row ) {
+                const auto& line = input[row];
+                if ( line.find('#') == line.npos ) {
+                        rows.insert(long(row));
+                }
+        }
+
+        for ( size_t col = 0; col != input[0].size(); ++col ) {
+                bool empty_col = true;
+                for ( const auto& line: input ) {
+                        if ( line[col] == '#' ) {
+                                empty_col = false;
+                        }
+                }
+                if ( empty_col ) {
+                        cols.insert(long(col));
+                }
+        }
+}
+
+void
+part2()
+{
+        auto input  = read_file("data/day11.txt");
+        auto points = find_points(input);
+
+        set<long> cols;
+        set<long> rows;
+
+        find_empty_rows_ans_cols(input, cols, rows);
+
+        auto scale = 1000000 - 1;
+        for ( auto& point: points ) {
+                const auto row = get<0>(point) + count_if(rows.begin(), rows.end(), [&](long row) { return row < get<0>(point); }) * scale;
+                const auto col = get<1>(point) + count_if(cols.begin(), cols.end(), [&](long col) { return col < get<1>(point); }) * scale;
+
+                point = { row, col };
+        }
+
+        solve(points);
+}
+
+int
+main()
+{
+        part1();
+        part2();
+}