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const std = @import("std");
pub fn main() !void {
const input = @embedFile("1.txt");
try std.fmt.format(std.io.getStdOut().writer(), "{}\n", .{try run(input)});
}
test {
std.debug.assert(try run(
\\3 4
\\4 3
\\2 5
\\1 3
\\3 9
\\3 3
) == 11);
}
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 lefts = std.ArrayList(u32).init(allocator);
defer lefts.deinit();
var rights = std.ArrayList(u32).init(allocator);
defer rights.deinit();
while (lines.next()) |line| {
if (line.len == 0) continue;
var words = std.mem.split(u8, line, " ");
const left = try std.fmt.parseInt(u32, words.next() orelse return error.InvalidInput, 10);
const right = try std.fmt.parseInt(u32, words.next() orelse return error.InvalidInput, 10);
try lefts.append(left);
try rights.append(right);
}
std.mem.sort(u32, lefts.items, {}, std.sort.asc(u32));
std.mem.sort(u32, rights.items, {}, std.sort.asc(u32));
var sum: u32 = 0;
for (lefts.items, rights.items) |l, r| {
sum += @max(l, r) - @min(l, r);
}
return sum;
}
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