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Vampire number: Difference between revisions
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14593825548650 is not a vampire number!
</pre>
=={{header|Rust}}==
<lang Rust>use std::cmp::{max, min};
static TENS: [u64; 20] = [
1,
10,
100,
1000,
10000,
100000,
1000000,
10000000,
100000000,
1000000000,
10000000000,
100000000000,
1000000000000,
10000000000000,
100000000000000,
1000000000000000,
10000000000000000,
100000000000000000,
1000000000000000000,
10000000000000000000,
];
/// Get the number of digits present in x
fn ndigits(mut x: u64) -> u64 {
let mut n = 0;
while x != 0 {
n += 1;
x /= 10;
}
n
}
fn dtally(mut x: u64) -> u64 {
let mut t = 0;
while x != 0 {
t += 1 << ((x % 10) * 6);
x /= 10;
}
t
}
/// Get a list of all fangs of x. Get only the first divider of each fang. The second one can be found simply with x / fang.
fn fangs(x: u64) -> Vec<u64> {
let mut nd = ndigits(x) as usize;
let mut fangs = vec![];
if nd & 1 != 1 {
nd /= 2;
let lo = max(TENS[nd - 1], (x + TENS[nd] - 2) / (TENS[nd] - 1));
let hi = min(x / lo, (x as f64).sqrt() as u64);
let t = dtally(x);
for a in lo..(hi + 1) {
let b = x / a;
if a * b == x && ((a % 10) > 0 || b % 10 > 0) && t == dtally(a) + dtally(b) {
fangs.push(a);
}
}
}
fangs
}
/// Pretty print the fangs of x
fn print_fangs(x: u64, fangs: Vec<u64>) {
print!("{} = ", x);
if fangs.is_empty() {
print!("is not vampiric");
} else {
for fang in fangs {
print!("{} x {}, ", fang, x / fang);
}
}
print!("\n");
}
fn main() {
println!("The first 25 vampire numbers are :");
let mut nfangs = 0;
let mut x = 1;
while nfangs < 25 {
let fangs = fangs(x);
if !fangs.is_empty() {
nfangs += 1;
print_fangs(x, fangs);
}
x += 1;
}
println!("\nSpecial requests :");
print_fangs(16758243290880, fangs(16758243290880));
print_fangs(24959017348650, fangs(24959017348650));
print_fangs(14593825548650, fangs(14593825548650));
}
#[test]
fn test() {
assert_eq!(
fangs(16758243290880),
vec![1982736, 2123856, 2751840, 2817360]
);
assert_eq!(
fangs(24959017348650),
vec![2947050, 2949705, 4125870, 4129587, 4230765]
);
assert_eq!(fangs(14593825548650), vec![]);
}</lang>
=={{header|Scala}}==
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