aoc 16

using namespace std;

int main() {
    auto start = absl::Now();
    string line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
    int curr = 0;
    int pos = -1;
    int next_char = 0;

    auto from_hex = [](char c) {
        if (c <='9') return c - '0';
        return c - 'A' + 10;
    };

    auto take = [&](int n) {
        long long x = 0;
        for(int i = 0; i < n; ++i) {
            x = x << 1;
            if (pos < 0) {
                pos = 3;
                curr = from_hex(line.at(next_char));
                ++next_char;
            }
            x += ((curr & 1 << pos) != 0) ? 1 : 0;
            curr &= ~(1 << pos);
            --pos;
        }
        return x;
    };

    function<long long(int*)> process;
    process = [&](int* bits) {
        take(3); // version
        auto id = take(3);
        if (bits != nullptr) {
            *bits -=6;
        }
        if (id == 4) {
            long long x = 0;
            while(true) {
                bool last = !take(1);
                x = x << 4;
                x += take(4);
                if (bits != nullptr) {
                    *bits -=5;
                }
                if (last) break;
            }
            return x;
        }
        else {
            std::vector<long long> ans;
            if (!take(1)) {
                int l = take(15);
                if (bits != nullptr) {
                    *bits -=16;
                    *bits -=l;
                }
                while(l > 0) {
                    ans.push_back(process(&l));
                }
            } else {
                int l = take(11);
                if (bits != nullptr) {
                    *bits -=12;
                }
                for (int i = 0; i < l; ++i) {
                    ans.push_back(process(bits));
                }
            }
            switch(id) {
                case 0: return absl::c_accumulate(ans, 0ll);
                case 1: return absl::c_accumulate(ans, 1ll, multiplies());
                case 2: return *absl::c_min_element(ans);
                case 3: return *absl::c_max_element(ans);
                case 5: return ans[0] > ans[1] ? 1ll : 0ll;
                case 6: return ans[0] < ans[1] ? 1ll : 0ll;
                case 7: return ans[0] == ans[1] ? 1ll: 0ll;
                default: throw invalid_argument("wrong id");
            }
        }
    };
    cout << process(nullptr) << endl;
    cout << absl::Now() - start << endl;

    return 0;
}