C++ universal/uniform/brace initialization

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| Words count in article 271

Universal/uniform/brace initialization introduced in C++11

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vector<vector<int>> res;
res.push_back({0, 1});
// res[0] is a vector

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vector<vector<int>> res;
res.push_back(vector<int>{0, 1});
// res[0] is a vector

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vector<list<int>> res;
res.push_back(list<int>{0, 1});
// res[0] is a list

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struct Student{
    int id, grade;
};

int main(){
    Student s{1, 68};
    
    vector<Student> v;
    v.push_back(Student{2, 90});
    v.push_back({3, 56});
    cout << v.size() << endl; // 2
    for(auto e: v) cout << e.id << ", "; cout << endl; // 2, 3,
}

One trap of universal initializations is shown here:

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vector<int> v1(4, 100); // [100, 100, 100, 100], fill constructor
vector<int> v2{4, 100}; // [4, 100], equivalent to vector<int> v = {4, 100};

vector<vector<int>> vv;
vv.push_back(vector<int>(4, 100));
vv.push_back(vector<int>{4, 100});
for(auto e: vv[0]) cout << e << ", "; cout << endl; // 100, 100, 100, 100, 
for(auto e: vv[1]) cout << e << ", "; cout << endl; // 4, 100,