1 files changed, 50 insertions, 0 deletions
diff --git a/day15/part1.cpp b/day15/part1.cpp
new file mode 100644
index 0000000..fb53753
--- /dev/null
+++ b/day15/part1.cpp
@@ -0,0 +1,50 @@
+#include <cstdio>
+#include <iostream>
+#include <set>
+#include <string>
+
+constexpr long Y = 2000000;
+
+int main()
+{
+    std::set<int> xs;
+    std::set<int> bs;
+    long px, py, bx, by;
+
+    do {
+        std::string line;
+        std::getline(std::cin, line);
+        if (std::cin.eof())
+            break;
+
+        auto a = sscanf(line.c_str(),
+            "Sensor at x=%ld, y=%ld: closest beacon is at x=%ld, y=%ld",
+            &px, &py, &bx, &by);
+
+        std::cout << px << ' ' << py << ' ' << bx << ' ' << by;
+
+        if (by == Y)
+            bs.insert(bx);
+
+        long ic = std::abs(px - bx) + std::abs(py - by);
+
+        if (Y < py - ic || Y > py + ic)
+            continue;
+
+        long spr = (ic - std::abs(py - Y));
+        for (long j = 0; j <= spr; ++j) {
+            xs.insert(px + j);
+            xs.insert(px - j);
+        }
+
+        std::cout << " -> " << xs.size() << std::endl;
+    } while (1);
+
+    for (auto& b : bs)
+        xs.erase(b);
+
+    std::cout << "Part 1: " << xs.size() << std::endl;
+
+    return 0;
+}
+