Truncatable primes: Difference between revisions
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Minor edit to C++ code
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m (Minor edit to C++ code) |
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=={{header|C++}}==
<lang cpp>#include <iostream>
#include "../library/sieve_of_eratosthenes.h"
bool is_left_truncatable(const sieve_of_eratosthenes& sieve, int p) {
int main()▼
return true;
}
bool is_right_truncatable(const sieve_of_eratosthenes& sieve, int p) {
return true;
}
▲int main() {
const int limit = 1000000;
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int largest_right = 0;
// find largest left truncatable prime
for (int p = limit; p >= 2; --p) {
▲ {
▲ if (!sieve.is_prime(p))
▲ continue;
▲ for (int n = 10, q = p; p > n; n *= 10)
▲ if (!sieve.is_prime(p % n) || q == p % n)
▲ q = p % n;
largest_left = p;
break;
Line 562 ⟶ 564:
}
// find largest right truncatable prime
for (int p = limit; p >= 2; --p) {
▲ {
▲ if (!sieve.is_prime(p))
▲ continue;
▲ for (int q = p/10; q > 0; q /= 10)
▲ if (!sieve.is_prime(q))
largest_right = p;
break;
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