Different ways of looping through a vector in c++

two_dimensional_vectors.cpp

/*
different ways of looping through a vector in c++
*/

#include <iostream>
#include <vector>
#include <numeric> // for style_four

using std::cout;
using std::vector;

int style_one(vector<int> v)
{
    int sum = 0;
    for(int i : v)
        sum += i;
    return sum;
}

int style_two(const vector<int> v)
{
    int sum = 0;
    for(int i = 0; i < v.size(); ++i)
        sum += v[i];
    return sum;
}

int style_three(const vector<int> &v)
{
    int sum = 0;
    for(auto i = v.begin(); i != v.end(); ++i)
        sum += i;
    return sum;
}

int style_four(const vector<int> &v)
{
    return std::accumulate(v.begin(), v.end(), 0);
}

int main() 
{
    vector<int> v {1, 2, 3};
    
}