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P3213.rs
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/*
Author : quickn (quickn.ga)
Email : [email protected]
*/
use std::str;
use std::io::{self, BufWriter, Write};
/* https://github.com/EbTech/rust-algorithms */
/// Same API as Scanner but nearly twice as fast, using horribly unsafe dark arts
/// **REQUIRES** Rust 1.34 or higher
pub struct UnsafeScanner<R> {
reader: R,
buf_str: Vec<u8>,
buf_iter: str::SplitAsciiWhitespace<'static>,
}
impl<R: io::BufRead> UnsafeScanner<R> {
pub fn new(reader: R) -> Self {
Self {
reader,
buf_str: Vec::new(),
buf_iter: "".split_ascii_whitespace(),
}
}
/// This function should be marked unsafe, but noone has time for that in a
/// programming contest. Use at your own risk!
pub fn token<T: str::FromStr>(&mut self) -> T {
loop {
if let Some(token) = self.buf_iter.next() {
return token.parse().ok().expect("Failed parse");
}
self.buf_str.clear();
self.reader
.read_until(b'\n', &mut self.buf_str)
.expect("Failed read");
self.buf_iter = unsafe {
let slice = str::from_utf8_unchecked(&self.buf_str);
std::mem::transmute(slice.split_ascii_whitespace())
}
}
}
}
use std::cmp::min;
fn main() {
let (stdin, stdout) = (io::stdin(), io::stdout());
let (mut scan, mut sout) = (UnsafeScanner::new(stdin.lock()), BufWriter::new(stdout.lock()));
let (mut cnt1, mut cnt2, mut cnt3): (usize, usize, usize) = (0, 0, 0);
let n: usize = scan.token();
for _i in 0..n {
let input: String = scan.token();
match input.as_str() {
"1/4" => {
cnt1 += 1;
},
"1/2" => {
cnt2 += 1;
},
_ => {
cnt3 += 1;
},
}
}
let mut res = 0;
// 1
let t1 = min(cnt1, cnt3);
res += t1;
cnt1 -= t1;
cnt3 -= t1;
// 2
let t2 = min(cnt1>>1, cnt2);
res += t2;
cnt1 -= t2<<1;
cnt2 -= t2;
// 3
let t3 = min(cnt1, cnt2);
res += t3;
cnt1 -= t3;
cnt2 -= t3;
// 4
res += ((cnt1 as f64)/4.0).ceil() as usize;
res += ((cnt2 as f64)/2.0).ceil() as usize;
res += cnt3;
writeln!(sout, "{}", res).ok();
}