dotfiles/lua/snippets/bit.lua

return [[
template<typename T>
struct BIT {
    int n;
    vector<T> c;
    BIT(size_t n) : n(n), c(n + 1) {}
    void add(size_t i, const T& k) {
        while (i <= n) {
            c[i] += k;
            i += lowbit(i);
        }
    }
    T getsum(size_t i) {
        T res = {};
        while (i) {
            res += c[i];
            i -= lowbit(i);
        }
        return res;
    }
};

]]