How to find the product of all numbers in a vector?

Yeah almost. There is a function that can fold. It needs to pass two additional parameters - the initial value (in the case of multiplication it is 1, this is logical) and what to do with the elements (multiply). Here is the code

#include <iostream> // std::cout #include <functional> // std::multiplies #include <numeric> // std::accumulate #include <vector> int main () { int init = 1; std::vector<int> numbers = {10,20,30}; std::cout << std::accumulate( numbers.begin(), // начало для умножения numbers.end(),// конец для умножения init,// начальное значение std::multiplies<int>());// готовая функция умножения. std::cout << '\n'; return 0; }