[Solved] Get the dot product of two vectors by functors and STL algorithms

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Just use std::inner_product:

live demo

#include <algorithm>
#include <iostream>
#include <iterator>
#include <ostream>
#include <numeric>
#include <cstdlib>
#include <vector>

using namespace std;

int main()
{
    vector<int> v1,v2;
    generate_n( back_inserter(v1), 256, rand );
    generate_n( back_inserter(v2), v1.size(), rand );
    cout << inner_product( v1.begin(), v1.end(), v2.begin(), 0 ) << endl;
}

Yes, that’s a good solution. But I don’t want to use any methods provided in numeric.h.

Just define your own dot_product:

live demo

template<typename InputIterator1,typename InputIterator2,typename ValueType>
ValueType dot_product( InputIterator1 first, InputIterator1 last, InputIterator2 another, ValueType init)
{
    while(first!=last)
    {
        init += (*first) * (*another) ;
        ++first;
        ++another;
    }
    return init;
}

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solved Get the dot product of two vectors by functors and STL algorithms