Product of min and max prime factors: Difference between revisions

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=={{header|C++}}==

<syntaxhighlight lang="cpp">#include <iomanip>

#include <iostream>

#include <utility>

auto min_max_prime_factors(unsigned int n) {

unsigned int min_factor = 1;

unsigned int max_factor = 1;

if ((n & 1) == 0) {

while ((n & 1) == 0)

n >>= 1;

min_factor = 2;

max_factor = 2;

}

for (unsigned int p = 3; p * p <= n; p += 2) {

if (n % p == 0) {

while (n % p == 0)

n /= p;

if (min_factor == 1)

min_factor = p;

max_factor = p;

}

}

if (n > 1) {

if (min_factor == 1)

min_factor = n;

max_factor = n;

}

return std::make_pair(min_factor, max_factor);

}

int main() {

std::cout << "Product of smallest and greatest prime factors of n for 1 to "

"100:\n";

for (unsigned int n = 1; n <= 100; ++n) {

auto p = min_max_prime_factors(n);

std::cout << std::setw(4) << p.first * p.second

<< (n % 10 == 0 ? '\n' : ' ');

}

}</syntaxhighlight>

{{out}}

<pre>

Product of smallest and greatest prime factors of n for 1 to 100:

1 4 9 4 25 6 49 4 9 10

121 6 169 14 15 4 289 6 361 10

21 22 529 6 25 26 9 14 841 10

961 4 33 34 35 6 1369 38 39 10

1681 14 1849 22 15 46 2209 6 49 10

51 26 2809 6 55 14 57 58 3481 10

3721 62 21 4 65 22 4489 34 69 14

5041 6 5329 74 15 38 77 26 6241 10

9 82 6889 14 85 86 87 22 7921 10

91 46 93 94 95 6 9409 14 33 10