Day 01

.gitignore

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+zig-cache

01/build.zig

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+const Builder = @import("std").build.Builder;
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+    const exe = b.addExecutable("01", "src/main.zig");
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const run_cmd = exe.run();
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+}

01/input

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01/src/main.zig

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+const std = @import("std");
+
+fn rocket(in: i64) i64 {
+    var x: i64 = @divFloor(in, 3) - 2;
+    if (x < 0) {
+        x = 0;
+    }
+
+    return x;
+}
+
+pub fn main() anyerror!void {
+    const file = std.io.getStdIn();
+    const stream = &file.inStream().stream;
+
+    var buf: [20]u8 = undefined;
+    var sum1: i64 = 0; // part 1
+    var sum2: i64 = 0; // part 2
+
+    while (try stream.readUntilDelimiterOrEof(&buf, '\n')) |line| {
+        const mass = try std.fmt.parseInt(i64, line, 10);
+        var rock = rocket(mass);
+        sum1 += rock;
+        while (rock > 0) {
+            sum2 += rock;
+            rock = rocket(rock);
+        }
+    }
+
+    std.debug.warn("Part 1: {}\n", sum1);
+    std.debug.warn("Part 2: {}\n", sum2);
+}
+