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Strong and weak primes: Difference between revisions
→{{header|Ruby}}
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37723 strong primes and 37780 weak primes below 1000000.
320991 strong primes and 321750 weak primes below 10000000.
</pre>
=={{header|Rust}}==
<lang rust>fn is_prime(n: i32) -> bool {
for i in 2..n {
if i * i > n {
return true;
}
if n % i == 0 {
return false;
}
}
n > 1
}
fn next_prime(n: i32) -> i32 {
for i in (n+1).. {
if is_prime(i) {
return i;
}
}
0
}
fn main() {
let mut n = 0;
let mut prime_q = 5;
let mut prime_p = 3;
let mut prime_o = 2;
print!("First 36 strong primes: ");
while n < 36 {
if prime_p > (prime_o + prime_q) / 2 {
print!("{} ",prime_p);
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("");
while prime_p < 1000000 {
if prime_p > (prime_o + prime_q) / 2 {
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("strong primes below 1,000,000: {}", n);
while prime_p < 10000000 {
if prime_p > (prime_o + prime_q) / 2 {
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("strong primes below 10,000,000: {}", n);
n = 0;
prime_q = 5;
prime_p = 3;
prime_o = 2;
print!("First 36 weak primes: ");
while n < 36 {
if prime_p < (prime_o + prime_q) / 2 {
print!("{} ",prime_p);
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("");
while prime_p < 1000000 {
if prime_p < (prime_o + prime_q) / 2 {
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("weak primes below 1,000,000: {}", n);
while prime_p < 10000000 {
if prime_p < (prime_o + prime_q) / 2 {
n += 1;
}
prime_o = prime_p;
prime_p = prime_q;
prime_q = next_prime(prime_q);
}
println!("weak primes below 10,000,000: {}", n);
}</lang>
<pre>
First 36 strong primes: 11 17 29 37 41 59 67 71 79 97 101 107 127 137 149 163 179 191 197 223 227 239 251 269 277 281 307 311 331 347 367 379 397 419 431 439
strong primes below 1,000,000: 37723
strong primes below 10,000,000: 320991
First 36 weak primes: 7 13 19 23 31 43 47 61 73 83 89 103 109 113 131 139 151 167 181 193 199 229 233 241 271 283 293 313 317 337 349 353 359 383 389 401
weak primes below 1,000,000: 37779
weak primes below 10,000,000: 321749
</pre>
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