STL_算法_for_each

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C++ Primer 学习中。。。

简单记录下我的学习过程 (代码为主)

所有容器适用

for_each(b,e,p)

1、使用for_each()算法遍历数据
2、使用for_each()和函数对象修改数据
3、使用for_each()的返回值

#include<iostream>#include<cstdio>#include<cstring>#include<vector>#include<algorithm>using namespace std;/*****************************************//所有容器适用for_each(b,e,p)使用for_each()算法遍历数据使用for_each()和函数对象修改数据使用for_each()的返回值*****************************************//*************************************************************************************std::for_each                   所有排序容器适用                           algorithm--------------------------------------------------------------------------------------template <class InputIterator, class Function>   Function for_each (InputIterator first, InputIterator last, Function f);//eg：template<class InputIterator, class Function>  Function for_each(InputIterator first, InputIterator last, Function f)  {    for ( ; first!=last; ++first ) f(*first);    return f;  }*************************************************************************************/void myfunction (int i){    cout << " " << i;}struct myclass{    void operator() (int i)    {        cout << " " << i;    }} myobject;class MeanVlaue{public:    MeanVlaue():num(0),sum(0){}    void operator() (int elem)    {        num++;        sum+=elem;    }    double value()    {        return static_cast<double>(sum)/static_cast<double>(num);    }    operator double()//重载的好处，简洁！    {        return static_cast<double>(sum)/static_cast<double>(num);    }private:    long num;    long sum;};template<class T>class AddValue{public:    AddValue(const T& v):theValue(v){}    void operator() (T& elem)const    {        elem+=theValue;    }private:    T theValue;};int main(){    vector<int> myvector;    myvector.push_back(10);    myvector.push_back(20);    myvector.push_back(30);    cout << "myvector contains:";    for_each (myvector.begin(), myvector.end(), myfunction);    // or:    cout << "\nmyvector contains:";    for_each (myvector.begin(), myvector.end(), myobject);    cout << endl;    MeanVlaue mv=for_each(myvector.begin(),myvector.end(),MeanVlaue());    cout<<"平均值："<<mv.value()<<endl;    for_each(myvector.begin(), myvector.end(), AddValue<int>(10));//参数可以自己改，eg：*(myvector.begin())    for_each (myvector.begin(), myvector.end(), myobject);    cout << endl;    double mv2=for_each(myvector.begin(),myvector.end(),MeanVlaue());    cout<<"平均值："<<mv2<<endl;    return 0;}

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