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factors.cpp
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factors.cpp
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/**
* @file
* @brief A program to calculate factors of a given number
* @author [Pradyumn Rahar](https://github.com/Hannibal404)
*/
#include <cassert>
#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
/**
* Function to calculate factors of a given number.
* @param n number whose factors we need to calculate.
* @return all factors of number.
*/
std::vector<int64_t> factors(int64_t n) {
std::vector<int64_t> ans;
if (n < 1) {
return ans;
}
ans.push_back(1);
int64_t d = 0;
if (n == 1) return ans;
for (int i = 2; i <= static_cast<int64_t>(sqrt(n));i++) {
if (n % i == 0) {
ans.push_back(i);
d = n / i;
if (d != i) {
ans.push_back(d);
}
}
}
ans.push_back(n);
sort(ans.begin(), ans.end());
return ans;
}
/** Test function
* @returns void
*/
void tests() {
std::cout << "Test 1:\t n=1\n";
std::vector<int64_t> out1 = {1};
assert(factors(1) == out1);
std::cout << "passed\n";
std::cout << "Test 2:\t n=5\n";
std::vector<int64_t> out2 = {1, 5};
assert(factors(5) == out2);
std::cout << "passed\n";
std::cout << "Test 3:\t n=24\n";
std::vector<int64_t> out3 = {1, 2, 3, 4, 6, 8, 12, 24};
assert(factors(24) == out3);
std::cout << "passed\n";
std::cout << "Test 4:\t n=-24\n";
std::vector<int64_t> out4 = {};
assert(factors(-24) == out4);
std::cout << "passed\n";
}
/** Main function
* @returns 0 on exit
*/
int main() {
tests();
return 0;
}