To assign values to a range, use any of the following standard algorithms:

• std::fill() to assign a value to all the elements of a range; the range is defined by a first and last forward iterator:

        std::vector<int> v(5);
        std::fill(v.begin(), v.end(), 42);
        // v = {42, 42, 42, 42, 42}

• std::fill_n() to assign values to a number of elements of a range; the range is defined by a first forward iterator and a counter that indicates how many elements should be assigned the specified value:

        std::vector<int> v(10);
        std::fill_n(v.begin(), 5, 42);
        // v = {42, 42, 42, 42, 42, 0, 0, 0, 0, 0}

• std::generate() to assign the value returned by a function to the elements of a range; the range is defined by a first and last forward iterator, and the function is invoked once for each element in the range:

        std::random_device rd{};
        std::mt19937 mt{ rd() };
        std::uniform_int_distribution<> ud{1, 10};
        std::vector<int> v(5);
        std::generate(v.begin(), v.end(), 
                      [&ud, &mt] {return ud(mt); }); 

• std::generate_n() to assign the value returned by a function to a number of elements of a range; the range is defined by a first forward iterator and a counter that indicates how many elements should be assigned the value from the function that is invoked once for each element:

        std::vector<int> v(5);
        auto i = 1;
        std::generate_n(v.begin(), v.size(), [&i] { return i*i++; });
        // v = {1, 4, 9, 16, 25}

• std::iota() to assign sequentially increasing values to the elements of a range; the range is defined by a first and last forward iterator, and the values are incremented using the prefix operator++ from an initial specified value:

        std::vector<int> v(5);
        std::iota(v.begin(), v.end(), 1);
        // v = {1, 2, 3, 4, 5}