1 files changed, 93 insertions, 0 deletions
diff --git a/day07.zig b/day07.zig
new file mode 100644
index 0000000..edc16df
--- /dev/null
+++ b/day07.zig
@@ -0,0 +1,93 @@
+const std = @import("std");
+const data = @embedFile("day07");
+
+var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
+const gpa = general_purpose_allocator.allocator();
+
+const eql = std.mem.eql;
+
+pub fn main() !void {
+    defer std.debug.assert(!general_purpose_allocator.deinit());
+
+    var lines = std.mem.tokenize(u8, data, "\n");
+
+    var fs = std.StringHashMap(usize).init(gpa);
+    defer {
+        var keyiter = fs.keyIterator();
+        while (keyiter.next()) |key| {
+            gpa.free(key.*);
+        }
+        fs.deinit();
+    }
+
+    var cwd = std.ArrayList([]const u8).init(gpa);
+    defer cwd.deinit();
+
+    _ = lines.next();
+    var root = try gpa.dupe(u8, "/");
+
+    while (lines.next()) |line| {
+        if (line.len == 0)
+            break;
+
+        if (eql(u8, line[0..4], "$ cd")) {
+            var parts = std.mem.tokenize(u8, line, " ");
+            _ = parts.next();
+            _ = parts.next();
+            var dir = parts.next().?;
+            
+            if (eql(u8, dir, "..")) {
+                _ = cwd.pop();
+            } else {
+                try cwd.append(dir);
+            }
+        } else if (eql(u8, line, "$ ls")) {
+            while (lines.peek()) |dirline| {
+                if (dirline[0] == '$') break;
+                _ = lines.next();
+                
+                if (eql(u8, dirline[0..4], "dir ")) continue;
+
+                var parts = std.mem.split(u8, dirline, " ");
+
+                var size = try std.fmt.parseInt(usize, parts.first(), 10);
+
+                try fs.put(root, (fs.get(root) orelse 0) + size);
+
+                var fullpath = std.ArrayList(u8).init(gpa);
+                defer fullpath.deinit();
+                for (cwd.items) |segment| {
+                    try fullpath.append('/');
+                    try fullpath.appendSlice(segment);
+
+                    var s = try gpa.dupe(u8, fullpath.items);
+
+                    var v = try fs.getOrPut(s);
+                    if (!v.found_existing) {
+                        v.value_ptr.* = size;
+                    } else {
+                        v.value_ptr.* += size;
+                        gpa.free(s);
+                    }
+                }
+            }
+        }
+    }
+
+    var part1: usize = 0;
+    var iter = fs.iterator();
+    while (iter.next()) |entry| {
+        if (entry.value_ptr.* <= 100_000)
+            part1 += entry.value_ptr.*;
+    }
+
+    var needed: usize = 30000000 - (70000000 - fs.get(root).?);
+    var part2: usize = 70000000;
+    var iter2 = fs.iterator();
+    while (iter2.next()) |entry| {
+        if (entry.value_ptr.* > needed)
+            part2 = std.math.min(part2, entry.value_ptr.*);
+    }
+
+    std.debug.print("{}\n{}\n", .{part1, part2});
+}