Submission #1167301

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Source Code Expand

use std::io::{BufRead, Write, stdin, stdout};

fn solve<R: BufRead, W: Write>(mut input: R, mut output: W) {
    let mut s = String::new();
    input.read_line(&mut s).unwrap();
    let x = s.trim().parse::<i64>().unwrap();
    let mut result = ((x * 2) as f64).sqrt().floor() as i64;
    if result * (result + 1) / 2 < x {
        result += 1;
    }
    writeln!(output, "{}", result).unwrap();
}

fn main() {
    let stdin = stdin();
    let stdout = stdout();
    solve(stdin.lock(), stdout.lock());
}

#[cfg(test)]
mod tests {
    fn test(input: &str, output: &str) {
        let mut v = Vec::<u8>::new();
        ::solve(input.as_bytes(), &mut v);
        assert_eq!(String::from_utf8(v).unwrap(), output);
    }
    #[test]
    fn case1() {
        test("6\n", "3\n");
    }
    #[test]
    fn case2() {
        test("2\n", "2\n");
    }
    #[test]
    fn case3() {
        test("11\n", "5\n");
    }
}

Submission Info

Judge Result