# How to Sum the Two Lowest Positive Integers in C++

## The challenge

Create a function that returns the sum of the two lowest positive numbers given an array of minimum 4 positive integers. No floats or non-positive integers will be passed.

For example, when an array is passed like `[19, 5, 42, 2, 77]`, the output should be `7`.

`[10, 343445353, 3453445, 3453545353453]` should return `3453455`.

## The solution in C++

Option 1:

``````#include <algorithm>
#include <vector>

long sumTwoSmallestNumbers(std::vector<int> numbers) {
std::sort(numbers.begin(), numbers.end());
return (long)numbers[0] + (long)numbers[1];
}
``````

Option 2:

``````#include <algorithm>

unsigned int sumTwoSmallestNumbers(std::vector<int> numbers) {
std::nth_element(begin(numbers), next(begin(numbers)), end(numbers));
return (unsigned int)(numbers[0] + numbers[1]);
}
``````

Option 3:

``````long sumTwoSmallestNumbers(std::vector<int> numbers) {
std::sort(numbers.begin(), numbers.end());
return (long long)numbers.at(0) + numbers.at(1);
}
``````

## Test cases to validate our solution

``````#include <algorithm>
#include <climits>
#include <cstdio>
#include <random>
#include <vector>

Describe(Tests)
{
It(BasicTest)
{
long expected = 13;
long actual = sumTwoSmallestNumbers({ 5, 8, 12, 19, 22 });
Assert::That(actual, Is().EqualTo(expected));
}

It(ExtendedTest1)
{
long expected = 6;
long actual = sumTwoSmallestNumbers({ 15, 28, 4, 2, 43 });
Assert::That(actual, Is().EqualTo(expected));
}

It(ExtendedTest2)
{
long expected = 10;
long actual = sumTwoSmallestNumbers({ 3, 87, 45, 12, 7 });
Assert::That(actual, Is().EqualTo(expected));
}

It(ExtendedTest3)
{
long expected = 4000000000;
long actual = sumTwoSmallestNumbers({ 2000000000, 2000000000, 2000000000, 2000000000, 2000000000 });
Assert::That(actual, Is().EqualTo(expected));
}

It(ExtendedTest4)
{
long expected = 5;
long actual = sumTwoSmallestNumbers({ 1000, 2, 3 });
Assert::That(actual, Is().EqualTo(expected));
}

It(RandomTests)
{
auto solution = [](std::vector<int> numbers) {
std::sort(numbers.begin(), numbers.end());
return (long)numbers[0] + (long)numbers[1];
};

std::default_random_engine generator{std::random_device()()};
std::uniform_int_distribution<int> distributor(1, INT_MAX);
std::uniform_int_distribution<std::vector<int>::size_type> sizeDistribution(4, 20);

for(int i = 0; i < 100; i++) {
int length = sizeDistribution(generator);

std::printf("Test for:\n");
std::vector<int> numbers;
for(int j = 0; j < length; j++) {
int n = distributor(generator);
numbers.push_back(n);

std::printf("%d", n);

if (j != length - 1) {
std::printf(", ");
}
}
std::printf("\n<hr>\n");
long expected = solution(numbers);
long actual = sumTwoSmallestNumbers(numbers);
Assert::That(actual, Is().EqualTo(expected));
}
}
};
``````