5 files changed, 39 insertions, 34 deletions

diff --git a/day-1/main.zig b/day-1/main.zig
index b2760fb..fa89e3f 100644
--- a/day-1/main.zig
+++ b/day-1/main.zig
@@ -1,18 +1,11 @@
 const std = @import("std");
+const slurp = @import("util/file.zig").slurp;
 
 var gpa = std.heap.GeneralPurposeAllocator(.{}){};
 const allocator = gpa.allocator();
 
 pub fn main() !void {
-    var path_buffer: [std.fs.MAX_PATH_BYTES]u8 = undefined;
-    const path = try std.fs.realpath("./input", &path_buffer);
-
-    const file = try std.fs.openFileAbsolute(path, .{});
-    defer file.close();
-
-    const file_size = (try file.stat()).size;
-
-    const file_buffer = try file.readToEndAlloc(allocator, file_size);
+    const file_buffer = try slurp(allocator, "./input");
     defer allocator.free(file_buffer);
 
     var iter = std.mem.split(u8, file_buffer, "\n");
diff --git a/day-1/main_1.zig b/day-1/main_1.zig
index 1a36e26..5e502d3 100644
--- a/day-1/main_1.zig
+++ b/day-1/main_1.zig
@@ -1,18 +1,12 @@
 const std = @import("std");
+const slurp = @import("util/file.zig").slurp;
+const min_idx = @import("util/mem.zig").min_idx;
 
 var gpa = std.heap.GeneralPurposeAllocator(.{}){};
 const allocator = gpa.allocator();
 
 pub fn main() !void {
-    var path_buffer: [std.fs.MAX_PATH_BYTES]u8 = undefined;
-    const path = try std.fs.realpath("./input", &path_buffer);
-
-    const file = try std.fs.openFileAbsolute(path, .{});
-    defer file.close();
-
-    const file_size = (try file.stat()).size;
-
-    const file_buffer = try file.readToEndAlloc(allocator, file_size);
+    const file_buffer = try slurp(allocator, "./input");
     defer allocator.free(file_buffer);
 
     var iter = std.mem.split(u8, file_buffer, "\n");
@@ -21,7 +15,7 @@ pub fn main() !void {
 
     while (iter.next()) |line| {
         if (line.len == 0) {
-            const lowest_u = lowest(i32, &max);
+            const lowest_u = min_idx(i32, &max);
             if (count > max[lowest_u]) {
                 max[lowest_u] = count;
             }
@@ -38,18 +32,3 @@ pub fn main() !void {
 
     std.debug.print("{d}\n", .{count});
 }
-
-fn lowest(comptime T: type, items: []const T) usize {
-    var lowest_u: usize = 0;
-    var previous: T = items[0];
-
-    for (items) |item, idx| {
-        if (item < previous) {
-            lowest_u = idx;
-        }
-
-        previous = item;
-    }
-
-    return lowest_u;
-}
diff --git a/day-1/util b/day-1/util
new file mode 120000
index 0000000..40c3fc5
--- /dev/null
+++ b/day-1/util
@@ -0,0 +1 @@
+../util
\ No newline at end of file
diff --git a/util/file.zig b/util/file.zig
new file mode 100644
index 0000000..90849e9
--- /dev/null
+++ b/util/file.zig
@@ -0,0 +1,15 @@
+const std = @import("std");
+
+/// Reads an entire file into memory, caller owns the returned slice.
+pub fn slurp(allocator: std.mem.Allocator, file_path: []const u8) ![]u8 {
+    var path_buffer: [std.fs.MAX_PATH_BYTES]u8 = undefined;
+    const path = try std.fs.realpath(file_path, &path_buffer);
+
+    const file = try std.fs.openFileAbsolute(path, .{});
+    defer file.close();
+
+    return try file.readToEndAlloc(
+        allocator,
+        (try file.stat()).size,
+    );
+}
diff --git a/util/mem.zig b/util/mem.zig
new file mode 100644
index 0000000..89ba67b
--- /dev/null
+++ b/util/mem.zig
@@ -0,0 +1,17 @@
+const std = @import("std");
+const math = std.math;
+
+/// Returns the position of the smallest number in a slice.
+pub fn min_idx(comptime T: type, slice: []const T) usize {
+    var best = slice[0];
+    var idx: usize = 0;
+
+    for (slice[1..]) |item, i| {
+        const possible_best = math.min(best, item);
+        if (best > possible_best) {
+            best = possible_best;
+            idx = i + 1;
+        }
+    }
+    return idx;
+}