2024: Day 2 complete

2024/day2.zig

@@ -0,0 +1,48 @@
+const std = @import("std");
+const print = std.debug.print;
+
+const util = @import("util.zig");
+
+fn isSafe(items: []const i16) bool {
+    if (!std.sort.isSorted(i16, items, {}, std.sort.asc(i16)) and
+        !std.sort.isSorted(i16, items, {}, std.sort.desc(i16))) return false;
+
+    for (1..items.len) |i| {
+        if (@abs(items[i] - items[i - 1]) > 3 or items[i] == items[i - 1]) return false;
+    }
+    return true;
+}
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+
+    const input = try util.readAllInput(2, allocator);
+
+    var safe: u16 = 0;
+    var safe_with_dampener: u16 = 0;
+    var lines = std.mem.tokenizeScalar(u8, input, '\n');
+    outer: while (lines.next()) |line| {
+        const levels = try util.inputToArrayList(i16, allocator, line);
+        defer levels.deinit();
+
+        // PART 1
+        if (isSafe(levels.items)) {
+            safe += 1;
+            continue;
+        }
+        // PART 2
+        for (0..levels.items.len) |i| {
+            var damp_levels = try levels.clone();
+            defer damp_levels.deinit();
+            _ = damp_levels.orderedRemove(i);
+            if (isSafe(damp_levels.items)) {
+                safe_with_dampener += 1;
+                continue :outer;
+            }
+        }
+    }
+
+    print("PART 1 - SAFE REPORTS:       {d}\n", .{safe});
+    print("PART 2 - SAFE WITH DAMPENER: {d}\n", .{safe + safe_with_dampener});
+}