AoC21/d01.cc

#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

int main(int argc, char *argv[]) {
    if (argc <= 1) return 1;

    vector<unsigned> numbers;
    {
        ifstream input(argv[1]);
        if (!input.is_open()) return 1;
        unsigned num;
        while (input >> num) {
            numbers.push_back(num);
        }
    }

    unsigned part1 = 0;
    for (size_t i = 1; i < numbers.size(); i++) {
        if (numbers[i] > numbers[i-1]) part1++;
    }
    cout << part1 << endl;

    unsigned part2 = 0;
    for (size_t i = 4; i < numbers.size(); i++) {
        unsigned win1 = numbers[i-1] + numbers[i-2] + numbers[i-3];
        unsigned win2 = numbers[i]   + numbers[i-1] + numbers[i-2];
        if (win2 > win1) part2++;
    }
    cout << part2 << endl;
}