2018/Day08/Day8B.cpp

#include <iostream>
#include <vector>

std::vector<int> read_input()
{
    std::vector<int> input;
    input.reserve(20000);

    int i = 0;
    while (std::cin >> i)
        input.push_back(i);

    return input;
}

int read_node(std::vector<int>::iterator &it)
{
    int child_count = *it++;
    int meta_count = *it++;
    int value = 0;

    if (child_count == 0) {
        for (int i = 0; i < meta_count; i++)
            value += *it++;

        return value;
    }

    std::vector<int> children;
    for (int i = 0; i < child_count; i++)
        children.push_back(read_node(it));

    for (int i = 0; i < meta_count; i++) {
        int index = *it++;
        if (index > 0 && index <= children.size())
            value += children[index - 1];
    }

    return value;
}

int main(int argc, char **argv)
{
    std::vector<int> input = read_input();
    auto iterator = input.begin();
    std::cout << read_node(iterator) << std::endl;
}