Range Sum Query - Immutable

class NumArray {
private:
    vector<int>* pData_;
public:
    NumArray(vector<int> &nums) {
        pData_ = &nums;
        const auto size = nums.size();
        auto& data = *pData_;
        if (size > 1){
            for (int i = 1; i != size; ++i){
                data[i] += data[i - 1];
            }
        }
    }
    
    int sumRange(int i, int j) {
        const auto& data = *pData_;
        return i == 0? data[j] : (data[j] - data[i - 1]);
    }
};