15: Add solution for Rust track exercise "Beer Song".

[?]

Aaw9nJhsNmfzFih9mKyNw9mV8CgERXJkRa1kK1Kx3LQH

Aug 22, 2021, 12:10 PM

6DOVDD66IQKHQJCQGIJX5B7675DUEAGUSHLMVCPWZEFMM6TFFBPAC

Dependencies

[2] QK6XE5XF 13: Add Rust track exercises "Beer Song", "Proverb", "Difference Of Squares", "Sum Of Multiples", "Grains", "Prime Factors", "Armstrong Numbers" and "Reverse String".

Change contents

replacement in rust/beer-song/tests/beer-song.rs at line 5

[2.35862]→[2.35862:36029](∅→∅)

assert_eq!(beer::verse(0), "No more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n");

[2.35862]

[2.36029]

assert_eq!(beer::verse(0), "No more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n");
replacement in rust/beer-song/tests/beer-song.rs at line 11

[2.36070]→[2.36070:36226](∅→∅)

assert_eq!(beer::verse(1), "1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n");

[2.36070]

[2.36226]

assert_eq!(beer::verse(1), "1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n");
replacement in rust/beer-song/tests/beer-song.rs at line 17

[2.36267]→[2.36267:36419](∅→∅)

assert_eq!(beer::verse(2), "2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n");

[2.36267]

[2.36419]

assert_eq!(beer::verse(2), "2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n");
replacement in rust/beer-song/tests/beer-song.rs at line 23

[2.36460]→[2.36460:36613](∅→∅)

assert_eq!(beer::verse(8), "8 bottles of beer on the wall, 8 bottles of beer.\nTake one down and pass it around, 7 bottles of beer on the wall.\n");

[2.36460]

[2.36613]

assert_eq!(beer::verse(8), "8 bottles of beer on the wall, 8 bottles of beer.\nTake one down and pass it around, 7 bottles of beer on the wall.\n");
replacement in rust/beer-song/tests/beer-song.rs at line 29

[2.36655]→[2.36655:37048](∅→∅)

assert_eq!(beer::sing(8, 6), "8 bottles of beer on the wall, 8 bottles of beer.\nTake one down and pass it around, 7 bottles of beer on the wall.\n\n7 bottles of beer on the wall, 7 bottles of beer.\nTake one down and pass it around, 6 bottles of beer on the wall.\n\n6 bottles of beer on the wall, 6 bottles of beer.\nTake one down and pass it around, 5 bottles of beer on the wall.\n");

[2.36655]

[2.37048]

assert_eq!(beer::sing(8, 6), "8 bottles of beer on the wall, 8 bottles of beer.\nTake one down and pass it around, 7 bottles of beer on the wall.\n\n7 bottles of beer on the wall, 7 bottles of beer.\nTake one down and pass it around, 6 bottles of beer on the wall.\n\n6 bottles of beer on the wall, 6 bottles of beer.\nTake one down and pass it around, 5 bottles of beer on the wall.\n");
replacement in rust/beer-song/tests/beer-song.rs at line 35

[2.37090]→[2.37090:37618](∅→∅)

assert_eq!(beer::sing(3, 0), "3 bottles of beer on the wall, 3 bottles of beer.\nTake one down and pass it around, 2 bottles of beer on the wall.\n\n2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n\n1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n\nNo more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n");

[2.37090]

[2.37618]

assert_eq!(beer::sing(3, 0), "3 bottles of beer on the wall, 3 bottles of beer.\nTake one down and pass it around, 2 bottles of beer on the wall.\n\n2 bottles of beer on the wall, 2 bottles of beer.\nTake one down and pass it around, 1 bottle of beer on the wall.\n\n1 bottle of beer on the wall, 1 bottle of beer.\nTake it down and pass it around, no more bottles of beer on the wall.\n\nNo more bottles of beer on the wall, no more bottles of beer.\nGo to the store and buy some more, 99 bottles of beer on the wall.\n");
edit in rust/beer-song/src/lib.rs at line 1

[2.37668]

[2.37669]

use std::convert::TryInto;

const DICT: [&str; 24] = [
"N", // 0
"o m", // 1
"ore", // 2
" bottle", // 3
"s", // 4
" of beer", // 5
" on", // 6
" th", // 7
"e ", // 8
"wall", // 9
", ", // 10
"n", // 11
".\n", // 12
"Go to", // 13
"st", // 14
" and ", // 15
"buy som", // 16
"m", // 17
"99", // 18
"Take", // 19
" it ", // 20
"down", // 21
"pass", // 22
"around", // 23
];

// Length for verse 3 onwards is just for the common substrings (i.e., excluding `n` and `n - 1`, so these need to be added back).
const LENGTHS: [usize; 4] = [129, 118, 114, 112];

fn integer_length(a: usize) -> usize {
((a as f64).log10() as usize) + 1
}

struct IndicesWithPrefixes<'a>(&'a [(&'a str, &'a [usize])]);

impl IndicesWithPrefixes<'_> {
fn generate_verse(&self, n: u32) -> String {
let n = n as usize;
let mut out = String::with_capacity(if n > 2 {
LENGTHS[3] + 2 * integer_length(n) + integer_length(n - 1)
} else { LENGTHS[n] } );
self.0.iter().for_each(|(prefix, indices)| {
out.push_str(prefix);
indices.iter().for_each(|index| out.push_str(DICT[*index]));
});
out
}
}
replacement in rust/beer-song/src/lib.rs at line 54

[2.37702]→[2.37702:37741](∅→∅)

unimplemented!("emit verse {}", n)

[2.37702]

[2.37741]

match n {
0 => {
let mut out = String::with_capacity(LENGTHS[0]);
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1, 2, 3, 4, 5, 12, 13, 7, 8, 14, 2, 15, 16, 8, 17, 2, 10, 18, 3, 4, 5, 6, 7, 8, 9, 12].iter().for_each(|index| out.push_str(DICT[*index]));
out
}
1 => {
let n_string = n.to_string();
IndicesWithPrefixes(&[(&n_string, &[3, 5, 6, 7, 8, 9, 10]), (&n_string, &[3, 5, 12, 19, 20, 21, 15, 22, 20, 23, 10, 11, 1, 2, 3, 4, 5, 6, 7, 8, 9, 12])]).generate_verse(n)
}
2 => {
let (n_string, m_string) = (n.to_string(), (n - 1).to_string());
IndicesWithPrefixes(&[(&n_string, &[3, 4, 5, 6, 7, 8, 9, 10]), (&n_string, &[3, 4, 5, 12, 19, 6, 8, 21, 15, 22, 20, 23, 10]), (&m_string, &[3, 5, 6, 7, 8, 9, 12])]).generate_verse(n)
}
_ => {
let (n_string, m_string) = (n.to_string(), (n - 1).to_string());
IndicesWithPrefixes(&[(&n_string, &[3, 4, 5, 6, 7, 8, 9, 10]), (&n_string, &[3, 4, 5, 12, 19, 6, 8, 21, 15, 22, 20, 23, 10]), (&m_string, &[3, 4, 5, 6, 7, 8, 9, 12])]).generate_verse(n)
}
}
}

fn integer_range_length(start: usize, end: usize) -> usize {
let (start_digits, end_digits) = (integer_length(start), integer_length(end));
let (a, b) = ((10_f64.powi(start_digits.try_into().unwrap()) - 1.0) as usize, 10_f64.powi((end_digits - 1).try_into().unwrap()) as usize);
(integer_length(a + 1)..=integer_length(b - 1)).fold(0, |acc, elem| acc + 9 * elem * (10_f64.powi((elem - 1).try_into().unwrap()) as usize)) + ((a - start + 1) * start_digits) + ((end - b + 1) * end_digits)
replacement in rust/beer-song/src/lib.rs at line 82

[2.37790]→[2.37790:37856](∅→∅)

unimplemented!("sing verses {} to {}, inclusive", start, end)

[2.37790]

[2.37856]

let (mut s, mut e) = (start, end);
if start < end {
s = end;
e = start;
}
match (s, e) {
(0, 0) => verse(0),
(1, 1) => verse(1),
(2, 2) => verse(2),
(_, _) => {
let mut out = String::with_capacity(
match (s, e) {
(1, 0) => LENGTHS[0] + LENGTHS[1],
(2, 0) => LENGTHS[0] + LENGTHS[1] + LENGTHS[2],
(2, 1) => LENGTHS[1] + LENGTHS[2],
(_, _) => (s as usize - 2) * LENGTHS[3] + integer_range_length(3, s as usize) + match e {
0 => LENGTHS[0] + LENGTHS[1] + LENGTHS[2],
1 => LENGTHS[1] + LENGTHS[2],
2 => LENGTHS[2],
_ => 0,
},
} + ((s - e) as usize)
);
if start < end {
out.push_str(&verse(e));
(e + 1..=s).for_each(|a| {
out.push_str("\n");
out.push_str(&verse(a));
});
} else {
out.push_str(&verse(s));
(e..=s - 1).rev().for_each(|a| {
out.push_str("\n");
out.push_str(&verse(a));
});
}
out
}
}