Day5

day5/zig/main.zig

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+const std = @import("std");
+
+const Range = struct { start: u64, end: u64 };
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    var stdin_buffer: [1024]u8 = undefined;
+    var stdin_reader = std.fs.File.stdin().reader(&stdin_buffer);
+
+    const stdin = &stdin_reader.interface;
+
+    const allocator = gpa.allocator();
+    var ranges = try std.ArrayList(Range).initCapacity(allocator, 1);
+    defer ranges.deinit(allocator);
+
+    var numbers = try std.ArrayList(u64).initCapacity(allocator, 1);
+    defer numbers.deinit(allocator);
+
+    var reading_ranges = true;
+
+    while (try stdin.takeDelimiter('\n')) |line| {
+        const line_trimmed = std.mem.trim(u8, line, "\n");
+
+        if (line.len == 0) {
+            reading_ranges = false;
+            continue;
+        }
+
+        if (reading_ranges) {
+            var it = std.mem.splitScalar(u8, line_trimmed, '-');
+
+            const start = try std.fmt.parseInt(u64, it.next().?, 10);
+            const end = try std.fmt.parseInt(u64, it.next().?, 10);
+
+            const range = Range{ .start = start, .end = end };
+
+            try ranges.append(allocator, range);
+        } else {
+            const number = try std.fmt.parseInt(u64, line_trimmed, 10);
+            try numbers.append(allocator, number);
+        }
+    }
+
+    var task1: u64 = 0;
+
+    for (numbers.items) |number| {
+        var spoiled = true;
+        for (ranges.items) |range| {
+            if (number <= range.end and number >= range.start) {
+                spoiled = false;
+                break;
+            }
+        }
+
+        if (!spoiled) {
+            task1 += 1;
+        }
+    }
+
+    var merged = true;
+
+    while (merged) {
+        merged = false;
+        for (ranges.items, 0..) |range1, i| {
+            for (ranges.items[i + 1 ..], i + 1..) |range2, j| {
+                // Non-overlapping
+                if (range1.end < range2.start or range1.start > range2.end) {
+                    continue;
+                }
+
+                // Calculate new range
+                const start = @min(range1.start, range2.start);
+                const end = @max(range1.end, range2.end);
+
+                ranges.items[i].start = start;
+                ranges.items[i].end = end;
+                _ = ranges.orderedRemove(j);
+                merged = true;
+                break;
+            }
+            if (merged) {
+                break;
+            }
+        }
+    }
+
+    var task2: u64 = 0;
+    for (ranges.items) |range| {
+        task2 += range.end - range.start + 1;
+    }
+
+    std.debug.print("{d}\n", .{task1});
+    std.debug.print("{d}\n", .{task2});
+}

day5/zig/sample.txt

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+3-5
+10-14
+16-20
+12-18
+
+1
+5
+8
+11
+17
+32