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const std = @import("std");
pub fn main() !void {
const input = @embedFile("2.txt");
try std.fmt.format(std.io.getStdOut().writer(), "{}\n", .{try run(input)});
}
test {
const value = try run(
\\7 6 4 2 1
\\1 2 7 8 9
\\9 7 6 2 1
\\1 3 2 4 5
\\8 6 4 4 1
\\1 3 6 7 9
);
std.debug.print("got {}\n", .{value});
std.debug.assert(value == 2);
}
pub fn run(input: []const u8) !u32 {
var lines = std.mem.split(u8, input, "\n");
var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
defer arena.deinit();
const allocator = arena.allocator();
var reports = std.ArrayList(std.ArrayList(u32)).init(allocator);
defer reports.deinit();
while (lines.next()) |line| {
if (line.len == 0) continue;
var report = std.ArrayList(u32).init(allocator);
var words = std.mem.split(u8, line, " ");
while (words.next()) |word| {
try report.append(try std.fmt.parseInt(u32, word, 10));
}
try reports.append(report);
}
var safe: u32 = 0;
for (reports.items) |report| {
const increasing = report.items[0] < report.items[1];
for (report.items[0 .. report.items.len - 1], report.items[1..]) |prev, curr| {
if ((prev < curr) != increasing) break;
if (prev == curr) break;
if (@max(prev, curr) - @min(prev, curr) > 3) break;
} else {
safe += 1;
}
}
return safe;
}
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