c++ 满足条件拷贝，容器扩容（copy_if）

#include <iostream>     // cout

#include <algorithm>    // copy_if, distance

#include <vector>       // vector

using namespace std;

int main () {

    vector<int> foo = {,,,-,-};

    vector<int> bar (foo.size());

    // copy only positive numbers:

    auto it = copy_if (foo.begin(), foo.end(), bar.begin(), [](int i){return !(i<);} );

    bar.resize(distance(bar.begin(),it));  // shrink container to new size

    cout << "bar contains:";

    for (int& x: bar) cout << ' ' << x;

    cout << '\n';

    return ;

}