(C++) std::partial_sum

 

std::partial_sum is an STL algorithm to calculate the partial sums of a container.

 

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#include <algorithm> #include <cassert> #include <numeric> #include <vector> int main() {   //Create a std::vector with five ones   const std::vector<int> v(5,1);   assert(v[0] == 1);   assert(v[1] == 1);   assert(v[2] == 1);   assert(v[3] == 1);   assert(v[4] == 1);   //Create a std::vector with the partial sums of five ones   std::vector<int> w;   std::partial_sum(v.begin(),v.end(),std::back_inserter(w));   assert(w[0] == 1); // 1   assert(w[1] == 2); // 1 + 1   assert(w[2] == 3); // 1 + 1 + 1   assert(w[3] == 4); // 1 + 1 + 1 + 1   assert(w[4] == 5); // 1 + 1 + 1 + 1 + 1   //Create a std::vector with the partial sums of   //the partial sums of those five ones   std::vector<int> x;   std::partial_sum(w.begin(),w.end(),std::back_inserter(x));   assert(x[0] == 1); // 1   assert(x[1] == 3); // 1 + 2   assert(x[2] == 6); // 1 + 2 + 3   assert(x[3] == 10); // 1 + 2 + 3 + 4   assert(x[4] == 15); // 1 + 2 + 3 + 4 + 5 }