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const std = @import("std");
const val = struct { n: u64, open: bool };
pub fn asc_val(_: void, a: val, b:val) bool {
return a.n < b.n;
}
pub fn main() !void {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();
const alloc = gpa.allocator();
const path = "input.txt";
const fp = try std.fs.cwd().openFile(path, .{.mode = std.fs.File.OpenMode.read_only});
defer fp.close();
var reader = fp.reader();
var list = std.ArrayList(val).init(alloc);
defer list.deinit();
var buffer: [256]u8 = undefined;
while(try reader.readUntilDelimiterOrEof(&buffer, '\n')) |line| {
if(line.len == 0) break;
if(std.mem.indexOf(u8, line, "-")) |ind| {
const low: u64 = try std.fmt.parseInt(u64, line[0 .. ind], 10);
const high: u64 = try std.fmt.parseInt(u64, line[ind + 1 ..], 10);
//no clue why this is required, since both are inclusive it should be fine, maybe better sorting would work here but im not certain
if(low == high){
continue;
}
try list.append(.{.n = high, .open = false});
try list.append(.{.n = low, .open = true});
}
}
std.mem.sort(val, list.items, {}, asc_val);
var count: i64 = 0;
var last_val: u64 = 0;
var fresh: u64 = 0;
for(list.items) |v| {
if(v.open){
count += 1;
if(count == 1) last_val = v.n;
} else {
count -= 1;
if(count == 0) fresh += v.n - last_val + 1;
}
}
std.debug.print("{d}\n", .{fresh});
}
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