Question

Suppose the vector I have is <1, 2, 3>, I want to get the accumulated values vector <1, 3, 6>. I guess that the C++ function partial_sum do that. But this function does not work when I execute (program bug). Is it partial_sum used correctly ?

vector<float> vv, vvSum;
vv.push_back(1); vv.push_back(2); vv.push_back(3);

partial_sum(vv.begin(), vv.end(), vvSum.begin(), plus<float>());

for(unsigned int i = 0; i < vvSum.size(); ++i)
{
    cout << vv[i] << " " << endl;
}

Answer 1

No, partial_sum is being used incorrectly.

The vvSum vector is empty. In that situation, vvSum.begin() is an end iterator, and thus cannot be used for output.

You can call vvSum.resize(vv.size()); to make it have the same size as the original, or use a std::back_inserter(vvSum) iterator, which increases the size of the container as needed.