algorithm与numeric的一些常用函数

numeric中的accumulated的基本用法：

来自：https://blog.csdn.net/u011499425/article/details/52756242

#include <vector>  
#include<numeric>
#include<iostream>
#include <string>  
using namespace std;
struct Grade
{
    string name;
    int grade;
};
int cmp(int a, Grade b)
{
    return a + b.grade;
}
int main()
{
    Grade subject[3] = {
        { "English", 80 },
    { "Biology", 70 },
    { "History", 90 }
    };

    //int sum = accumulate(subject, subject + 3, 0, [](int a, Grade b) {return a + b.grade; });
    int sum = accumulate(subject, subject + 3, 0, cmp);
    cout << sum << endl;

    system("pause");
    return 0;
}

algorithm的count:利用等于操作符，把标志范围内的元素与输入值比较，返回相等元素个数。

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
    int a[] = { 1, 2, 2, 6 };
    int k = count(a, a + 4,2);
    cout << k << endl;
    return 0;
}

 unique:去重；