STL - General Questions

What will be the output of the program?

#include <iostream>
using namespace std;
#include <deque>
int main() {
    deque<int> d;
    d.push_back(2); d.push_front(1); d.push_back(3);
    cout << d.front() << d.back() << d.size() << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
#include <vector>
int main() {
    vector<int> v = {1, 2, 3};
    v.pop_back();
    v.insert(v.begin(), 9);
    for (int x : v) cout << x;
    cout << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
#include <vector>
#include <numeric>
int main() {
    vector<int> v = {1, 2, 3, 4};
    cout << accumulate(v.begin(), v.end(), 10) << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
#include <vector>
#include <algorithm>
int main() {
    vector<int> v = {4, 8, 15, 16, 23, 42};
    cout << (find(v.begin(), v.end(), 16) - v.begin()) << endl;
    return 0;
}

What will be the output of the program?

#include <iostream>
using namespace std;
#include <set>
int main() {
    set<int> s = {5, 1, 3};
    s.insert(3);
    s.erase(1);
    for (int x : s) cout << x;
    cout << endl;
    return 0;
}