2023/09/src/part2.cpp


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#include <numeric>
#include <fstream>
#include <iostream>
#include <sstream>
#include <vector>

void solve(std::vector<int> v, int& answer)
{
    for (int a = 0; a < v.size() - 1; ++a)
    {
        answer += v[a];
        for (int b = v.size() - 1; b > a; --b)
        {
            v[b] = v[b-1] - v[b];
        }
    }
}

int main(int argc, char* argv[])
{
    int answer{};

    std::ifstream input{ argv[1] };
    if (input.is_open())
    {
        std::string line;
        while (not std::getline(input,line).eof())
        {
            int n;
            std::vector<int> v{};
            std::istringstream sline{ line };
            while(sline >> n)
            {
                v.push_back(n);
            }

            solve(std::move(v), answer);
        }
    }
    input.close();

    std::cout << answer << std::endl;
    return 0;
}