Day3

day3/zig/main.zig

@@ -0,0 +1,57 @@
+const std = @import("std");
+
+const Lv = struct { value: u8, position: usize };
+
+pub fn main() !void {
+    var stdin_buffer: [1024]u8 = undefined;
+    var stdin_reader = std.fs.File.stdin().reader(&stdin_buffer);
+
+    const stdin = &stdin_reader.interface;
+
+    var task1: u32 = 0;
+    var task2: u64 = 0;
+
+    while (try stdin.takeDelimiter('\n')) |line| {
+        var highest_joltage: u32 = 0;
+        for (line, 0..) |c1, i| {
+            for (line[i + 1 ..]) |c2| {
+                const c_arr = [_]u8{ c1, c2 };
+                const num = try std.fmt.parseInt(u32, &c_arr, 10);
+
+                if (num > highest_joltage) {
+                    highest_joltage = num;
+                }
+            }
+        }
+
+        var chars: [12]u8 = undefined;
+        var i: usize = 0;
+        var current: usize = 0;
+
+        while (i < 12) : (i += 1) {
+            const largest = find_largest(line[current .. line.len - 11 + i]);
+            current += largest.position + 1;
+            chars[i] = largest.value;
+        }
+        const num = try std.fmt.parseInt(u64, &chars, 10);
+
+        task2 += num;
+        task1 += highest_joltage;
+    }
+
+    std.debug.print("{d}\n", .{task1});
+    std.debug.print("{d}\n", .{task2});
+}
+
+fn find_largest(values: []const u8) Lv {
+    var largest_value: u8 = 0;
+    var largest_position: usize = 0;
+    for (values, 0..) |value, i| {
+        if (value > largest_value) {
+            largest_position = i;
+            largest_value = value;
+        }
+    }
+
+    return Lv{ .value = largest_value, .position = largest_position };
+}