Practical numbers: Difference between revisions
Added Rust solution
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672 is practical? True
720 is practical? True</pre>
=={{header|Rust}}==
{{trans|Phix}}
<lang rust>fn sum_of_any_subset(n: isize, f: &[isize]) -> bool {
let len = f.len();
if len == 0 {
return false;
}
if f.contains(&n) {
return true;
}
let mut total = 0;
for i in 0..len {
total += f[i];
}
if n == total {
return true;
}
if n > total {
return false;
}
let d = n - f[len - 1];
let g = &f[0..len - 1];
(d > 0 && sum_of_any_subset(d, g)) || sum_of_any_subset(n, g)
}
fn proper_divisors(n: isize) -> Vec<isize> {
let mut f = vec![1];
let mut i = 2;
loop {
let i2 = i * i;
if i2 > n {
break;
}
if n % i == 0 {
f.push(i);
if i2 != n {
f.push(n / i);
}
}
i += 1;
}
f.sort();
f
}
fn is_practical(n: isize) -> bool {
let f = proper_divisors(n);
for i in 1..n {
if !sum_of_any_subset(i, &f) {
return false;
}
}
true
}
fn shorten(v: &[isize], n: usize) -> String {
let mut str = String::new();
let len = v.len();
let mut i = 0;
if n > 0 && len > 0 {
str.push_str(&v[i].to_string());
i += 1;
}
while i < n && i < len {
str.push_str(", ");
str.push_str(&v[i].to_string());
i += 1;
}
if len > i + n {
if n > 0 {
str.push_str(", ...");
}
i = len - n;
}
while i < len {
str.push_str(", ");
str.push_str(&v[i].to_string());
i += 1;
}
str
}
fn main() {
let from = 1;
let to = 333;
let mut practical = Vec::new();
for n in from..=to {
if is_practical(n) {
practical.push(n);
}
}
println!(
"Found {} practical numbers between {} and {}:\n{}",
practical.len(),
from,
to,
shorten(&practical, 10)
);
for n in &[666, 6666, 66666, 672, 720, 222222] {
if is_practical(*n) {
println!("{} is a practical number.", n);
} else {
println!("{} is not practical number.", n);
}
}
}</lang>
{{out}}
<pre>
Found 77 practical numbers between 1 and 333:
1, 2, 4, 6, 8, 12, 16, 18, 20, 24, ..., 288, 294, 300, 304, 306, 308, 312, 320, 324, 330
666 is a practical number.
6666 is a practical number.
66666 is not practical number.
672 is a practical number.
720 is a practical number.
222222 is a practical number.
</pre>
=={{header|Visual Basic .NET}}==
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