C++ STL 中的数值算法示例讲解

    vector<int> a(10);
    iota(begin(a), end(a), 5);

    for (auto x : a) {
        cout << x << " ";
    }

    vector<int> a(10);
    iota(begin(a), end(a), 1);

    cout << accumulate(begin(a), end(a), 0) << "\n";  // 计算从1加到10的和，从0开始加

template <class InputIterator, class T>
   T accumulate (InputIterator first, InputIterator last, T init)
{
  while (first!=last) {
    init = init + *first;  // or: init=binary_op(init,*first) for the binary_op version
    ++first;
  }
  return init;
}

    vector<int> a(10);
    iota(begin(a), end(a), 1);

    cout << accumulate(begin(a), end(a), 1, multiplies<int>()) << "\n";  // 计算从1加到10的乘积，从1开始乘

    vector<int> a(5);
    iota(begin(a), end(a), 1);

    partial_sum(begin(a), end(a), begin(a)); // 求a的前缀和，赋值给a数组（第三个参数）

    for (auto x : a) {
        cout << x << " ";
    }

    partial_sum(begin(a), end(a), begin(a), multiplies<int>());

vector<int> a{1, 4, 5, 100, 40};

adjacent_difference(begin(a), end(a), begin(a)); // 求a数组相邻元素的差，赋值给a数组（第三个参数）

for (auto x : a) {
    cout << x << " ";
}

adjacent_difference(begin(a), end(a), begin(a), multiplies<int>());

    vector<int> a(3);
    iota(begin(a), end(a), 1);

    cout << inner_product(begin(a), end(a), begin(a), 10) << "\n"; // 从初值10开始加上序列各元素的内积

    vector<int> a{1, 2, 3};
    vector<int> b{2, 3, 4};

    // 1 * 2 + 2 * 3 + 3 * 4
    cout << inner_product(begin(a), end(a), begin(b), 0) << "\n";

    vector<int> a{1, 2, 3};
    vector<int> b{2, 3, 4};

    cout << inner_product(begin(a), end(a), begin(b), 1
                        , multiplies<int>(), minus<int>()) << "\n";
                            // 原来的加法 +  // 原来的乘法 *
                            // 计算 (1 - 2) * (2 - 3) * (3 - 4) = -1