修改BOOST_FOREACH中向量的内容

#include<iostream>
#include<vector>

int main() {
    std::vector<int> vec = {1, 2, 3, 4, 5};

    for (std::vector<int>::iterator it = vec.begin(); it != vec.end(); ++it) {
        *it *= 2;
    }

    for (int i : vec) {
        std::cout << i << " ";
    }

    return 0;
}

#include<iostream>
#include<vector>

int main() {
    std::vector<int> vec = {1, 2, 3, 4, 5};

    for (int& i : vec) {
        i *= 2;
    }

    for (int i : vec) {
        std::cout << i << " ";
    }

    return 0;
}