STL：通用数值计算

STL：通用数值计算

参考文献《大道至简：C++STL》

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

void print(int elem)
{
    cout << elem << " ";
}

int defop(int ori, int elem)
{
    return ori * 2 + elem;
}

int defop2(int initv, int elem)
{
    return initv + elem;
}

int main()
{
    vector<int> vec = {1, 2, 3, 4, 5};
    vector<int> vec2 = {3, 4, 5, 6, 7};

/*求和*/

    int accval;
    accval = accumulate(vec.begin(), vec.end(), 0);
    printf("sccval:%d\n", accval);
    accval = accumulate(vec.begin(), vec.end(), 0, defop);
    printf("accval:%d\n", accval);

/*内积*/

    int inprodval;
    inprodval = inner_product(vec.begin(), vec.end(), vec2.begin(), 0);
    printf("inprodval:%d\n", inprodval);
    inprodval = inner_product(vec.begin(), vec.end(), vec2.begin(), 0, defop2, defop);
    printf("inprodval:%d\n", inprodval);

    //等价于
    inprodval = 0;
    for(int i = 0; i < vec.size(); i++)
    {
        inprodval += vec[i] * 2 + vec2[i];
    }
    printf("inprodval:%d\n", inprodval);

/*部分和*/

    vector<int> vec3, vec4;
    partial_sum(vec.begin(), vec.end(), back_inserter(vec3));
    for_each(vec3.begin(), vec3.end(), print);      //1 3 6 10 15
    cout << endl;
    partial_sum(vec.begin(), vec.end(), back_inserter(vec4), defop);
    for_each(vec4.begin(), vec4.end(), print);      //1 4 11 26 57
    cout << endl;

/*序列相邻差*/

    vector<int> vec5, vec6;
    adjacent_difference(vec.begin(), vec.end(), back_inserter(vec5));
    for_each(vec5.begin(), vec5.end(), print);      //1 1 1 1 1
    cout << endl;
    adjacent_difference(vec.begin(), vec.end(), back_inserter(vec6), defop);
    for_each(vec6.begin(), vec6.end(), print);      //1 5 8 11 14
    cout << endl;

    return 0;
}