Practice Questions — STL Containers - vector, list, map, set, stack, queue

vector<int> v = {10, 20, 30};
v.push_back(40);
cout << v.size() << " " << v[3];

set<int> s = {5, 2, 8, 2, 1, 5};
cout << s.size();

set<int> s = {30, 10, 20};
for (int x : s) cout << x << " ";

stack<int> st;
st.push(10);
st.push(20);
st.push(30);
cout << st.top();
st.pop();
cout << " " << st.top();

queue<int> q;
q.push(10);
q.push(20);
q.push(30);
cout << q.front() << " " << q.back();

map<string, int> m;
m["Kiran"] = 78;
m["Arjun"] = 85;
for (auto& [k, v] : m) cout << k << " ";

vector<int> v;
v.reserve(10);
v.push_back(1);
v.push_back(2);
cout << v.size() << " " << v.capacity();

priority_queue<int> pq;
pq.push(10);
pq.push(50);
pq.push(30);
pq.push(20);
cout << pq.top();
pq.pop();
cout << " " << pq.top();

priority_queue<int, vector<int>, greater<int>> pq;
pq.push(30);
pq.push(10);
pq.push(50);
cout << pq.top();

multiset<int> ms = {3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5};
cout << ms.count(5) << " " << ms.count(7);

map<string, int> m;
m["Priya"] = 92;
m["Arjun"] = 85;
cout << m.size() << endl;
m["Ravi"];  // Access non-existent key
cout << m.size() << " " << m["Ravi"];

set<int> s = {1, 3, 5, 7, 9};
auto lb = s.lower_bound(4);
auto ub = s.upper_bound(7);
cout << *lb << " " << *ub;

map<int, string> m = {{3, "C"}, {1, "A"}, {2, "B"}};
auto it = m.begin();
cout << it->first << ":" << it->second << " ";
++it; ++it;
cout << it->first << ":" << it->second;

vector<int> v;
cout << v.size() << " ";
v.resize(5, 42);
cout << v.size() << " " << v[0] << " " << v[4] << " ";
v.resize(3);
cout << v.size() << " " << v[2];

deque<int> dq = {20, 30, 40};
dq.push_front(10);
dq.push_back(50);
dq.pop_front();
dq.pop_back();
cout << dq.front() << " " << dq.back() << " " << dq[1];

set<int> s = {5, 10, 15, 20, 25};
auto it = s.find(15);
if (it != s.end()) s.erase(it);
for (int x : s) cout << x << " ";

map<int, string> m = {{1,"one"}, {2,"two"}, {3,"three"}};
for (auto it = m.begin(); it != m.end(); ) {
    if (it->first % 2 == 0)
        it = m.erase(it);
    else
        ++it;
}
for (auto& [k, v] : m) cout << k << ":" << v << " ";

vector<int> v = {1, 2, 3};
v.insert(v.end(), {4, 5, 6});
cout << v.size() << " " << v.back();

priority_queue<pair<int,string>, vector<pair<int,string>>, greater<pair<int,string>>> pq;
pq.push({3, "Kiran"});
pq.push({1, "Arjun"});
pq.push({2, "Priya"});
cout << pq.top().second;

vector<int> v;
cout << v.empty() << " ";
v.push_back(10);
cout << v.empty() << " " << v.front();

vector<int> v = {1, 2, 3, 4, 5};
v.pop_back();
v.pop_back();
cout << v.size() << " " << v.back();

set<int> s = {10, 20, 30};
s.insert(20);
s.insert(40);
cout << s.size();

stack<char> st;
st.push('A');
st.push('B');
st.push('C');
st.pop();
cout << st.top() << " " << st.size();

map<char, int> freq;
string s = "banana";
for (char c : s) freq[c]++;
cout << freq['a'] << " " << freq['n'] << " " << freq.size();

set<int> s = {1, 2, 3, 4, 5};
s.erase(3);
cout << s.count(3) << " " << s.size();

vector<int> v = {10, 20, 30};
v.insert(v.begin() + 1, 15);
for (int x : v) cout << x << " ";

unordered_map<string, int> m;
m["Arjun"] = 85;
m["Priya"] = 92;
cout << (m.find("Arjun") != m.end()) << " ";
cout << (m.find("Kiran") != m.end());

priority_queue<int> pq;
for (int x : {4, 1, 7, 3, 8, 2}) pq.push(x);
int sum = 0;
while (pq.size() > 3) {
    sum += pq.top();
    pq.pop();
}
cout << sum << " " << pq.top();

multimap<string, int> mm;
mm.insert({"Arjun", 85});
mm.insert({"Arjun", 90});
mm.insert({"Arjun", 78});
mm.insert({"Priya", 92});
cout << mm.count("Arjun") << " " << mm.size();

set<int> s = {10, 20, 30, 40, 50};
auto it1 = s.lower_bound(25);
auto it2 = s.upper_bound(30);
auto it3 = s.lower_bound(60);
cout << *it1 << " " << *it2 << " " << (it3 == s.end());

map<int, int> m = {{1, 10}, {2, 20}, {3, 30}};
m[2] = 25;
m.erase(1);
m.insert({4, 40});
for (auto& [k, v] : m) cout << k << ":" << v << " ";

unordered_map<string, int> m;
m["a"] = 1;
m["b"] = 2;
m["c"] = 3;
cout << m.size() << " " << m.count("b") << " " << m.count("d");

set<int> a = {1, 2, 3, 4, 5};
set<int> b = {3, 4, 5, 6, 7};
vector<int> result;
set_intersection(a.begin(), a.end(), b.begin(), b.end(), back_inserter(result));
for (int x : result) cout << x << " ";

stack<int> st;
st.push(1);
st.push(2);
st.push(3);
cout << st.size() << " ";
while (!st.empty()) {
    cout << st.top() << " ";
    st.pop();
}

queue<string> q;
q.push("Arjun");
q.push("Priya");
q.push("Kiran");
q.pop();
cout << q.front() << " " << q.size();