Strange unique prime triplets: Difference between revisions
Added Rust solution
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</pre>
=={{header|Rust}}==
<lang rust>fn prime_sieve(limit: usize) -> Vec<bool> {
let mut sieve = vec![true; limit];
if limit > 0 {
sieve[1] = false;
}
for i in (0..limit).step_by(2) {
sieve[i] = false;
}
let mut p = 3;
loop {
let mut q = p * p;
if q >= limit {
break;
}
if sieve[p] {
let inc = 2 * p;
while q < limit {
sieve[q] = false;
q += inc;
}
}
p += 2;
}
sieve
}
fn strange_unique_prime_triplets(limit: usize, verbose: bool) {
let mut primes = Vec::new();
if limit < 8 {
return;
}
let sieve = prime_sieve(limit * 3);
for p in (3..limit).step_by(2) {
if sieve[p] {
primes.push(p);
}
}
if verbose {
println!("Strange unique prime triplets < {}:", limit);
}
let mut count = 0;
let n = primes.len();
for i in 0..n - 2 {
for j in i + 1..n - 1 {
for k in j + 1..n {
let sum = primes[i] + primes[j] + primes[k];
if sieve[sum] {
count += 1;
if verbose {
println!(
"{:2} + {:2} + {:2} = {:2}",
primes[i], primes[j], primes[k], sum
);
}
}
}
}
}
println!(
"Count of strange unique prime triplets < {} is {}.",
limit, count
);
}
fn main() {
strange_unique_prime_triplets(30, true);
strange_unique_prime_triplets(1000, false);
}</lang>
{{out}}
<pre>
Strange unique prime triplets < 30:
3 + 5 + 11 = 19
3 + 5 + 23 = 31
3 + 5 + 29 = 37
3 + 7 + 13 = 23
3 + 7 + 19 = 29
3 + 11 + 17 = 31
3 + 11 + 23 = 37
3 + 11 + 29 = 43
3 + 17 + 23 = 43
5 + 7 + 11 = 23
5 + 7 + 17 = 29
5 + 7 + 19 = 31
5 + 7 + 29 = 41
5 + 11 + 13 = 29
5 + 13 + 19 = 37
5 + 13 + 23 = 41
5 + 13 + 29 = 47
5 + 17 + 19 = 41
5 + 19 + 23 = 47
5 + 19 + 29 = 53
7 + 11 + 13 = 31
7 + 11 + 19 = 37
7 + 11 + 23 = 41
7 + 11 + 29 = 47
7 + 13 + 17 = 37
7 + 13 + 23 = 43
7 + 17 + 19 = 43
7 + 17 + 23 = 47
7 + 17 + 29 = 53
7 + 23 + 29 = 59
11 + 13 + 17 = 41
11 + 13 + 19 = 43
11 + 13 + 23 = 47
11 + 13 + 29 = 53
11 + 17 + 19 = 47
11 + 19 + 23 = 53
11 + 19 + 29 = 59
13 + 17 + 23 = 53
13 + 17 + 29 = 59
13 + 19 + 29 = 61
17 + 19 + 23 = 59
19 + 23 + 29 = 71
Count of strange unique prime triplets < 30 is 42.
Count of strange unique prime triplets < 1000 is 241580.
</pre>
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