【C++\408考研必备】模板函数、内存分配、标准模板

//版本1
template <class InputIterator,class T>
T accumulate(InputIterator first,InputIterator last,T init){
    for(;first != last; ++first){
        init += *first; //将每个元素数值累加到init身上
    }
    return init;
}
 
//版本2
template <class InputIterator,class T,class BinaryOperation>
T accumulate(InputIterator first,InputIterator last,T init,
             BinaryOperation binary_op){
    for(;first!=last;++first){
        init = binary_op(init, *first);//对每一个元素执行二元操作
    }
    return init;
}

#include <iostream>   //std::cout
#include <functional> //std::minuc
#include <numeric>    //std::accumulate
 
int my_function(int x,int y){return x + 2*y;}
struct my_class{
    int operator()(int x,int y){
        return x + 3*y;
    }
}my_object;
 
int main(){
    int init = 100;
    int numbers[] = {10,20,30};
//    std::cout << << std::endl;
    std::cout << "using default accumulate" << std::endl;
    std::cout << std::accumulate(numbers,numbers+3,init) << std::endl;
 
    std::cout << "using functional's accumulate" << std::endl;
    std::cout << std::accumulate(numbers,numbers+3,init,std::minus<int>()) << std::endl;
 
    std::cout << "using custom function" << std::endl;
    std::cout << std::accumulate(numbers,numbers+3,init, my_function) << std::endl;
 
    std::cout << "using custom object" << std::endl;
    std::cout << std::accumulate(numbers,numbers+3,init, my_object) << std::endl;
 
}