pir

pir.rs

#![allow(dead_code)]

use std::iter::repeat;

fn main() {}

fn pir(n: u32) -> String {
    let mut x = 1;

    (0..n)
        .map(|i| next_line(n, i, &mut x))
        .collect::<Vec<String>>()
        .join("\n")
}

#[inline]
fn next_line(n: u32, i: u32, x: &mut usize) -> String {
    line(next_space(n, i), next_x(x))
}

#[inline]
fn next_space(n: u32, i: u32) -> usize {
    (n - i - 1) as usize
}

fn next_x(x: &mut usize) -> usize {
    let ol_x = *x;
    *x += 2;
    ol_x
}

#[inline]
fn line(space: usize, x: usize) -> String {
    let space_l = repeat(' ').take(space);
    let x = repeat('x').take(x);
    let space_r = repeat(' ').take(space);

    space_l.chain(x)
        .chain(space_r)
        .collect::<String>()
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn text1() {
        assert_eq!(
            pir(3), [
                "  x  ", //2, 1
                " xxx ", //1, 3,
                "xxxxx" // 0, 5
            ].join("\n")
        )
    }

    #[test]
    fn text2() {
        assert_eq!(
            pir(2), [
                " x ",
                "xxx",
            ].join("\n")
        )
    }

    #[test]
    fn text3() {
        assert_eq!(
            pir(4), [
                "   x   ",
                "  xxx  ",
                " xxxxx ",
                "xxxxxxx",
            ].join("\n")
        )
    }
}