C++ Map and Multimap

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Question 1

What will be the output of the following C++ program?

C++

#include <bits/stdc++.h>
using namespace std;

int main() {
    multimap<int, int> mp;

    mp.insert({2, 30});
    mp.insert({1, 40});
    mp.insert({3, 60});
    mp.insert({1, 20});
    mp.insert({5, 50});

    auto it = mp.equal_range(1);

    for (auto itr = it.first; itr != it.second; ++itr) {
        cout << itr->first << '\t' << itr->second << '\n';
    }
    return 0;
}

1 40
1 20
3 60
1 20
1 40
2 30
3 60
5 50

Question 2

What will be the output of the following C++ program?

C++

#include <iostream>
#include <map>
using namespace std;

int main() {
    multimap<char, int> sample;

    sample.insert(make_pair('a', 10));
    sample.insert(make_pair('b', 20));
    sample.insert(make_pair('b', 30));
    sample.insert(make_pair('c', 40));
    sample.insert(make_pair('c', 50));

    cout << sample.rbegin()->first << " = " << sample.rbegin()->second;
}

c = 50
c = 40
b = 30
a = 10

Question 3

Can you use the [] operator to access elements in a std::multimap?

Yes, it returns a reference to the element with the given key
Yes, it returns a pointer to the element with the given key
No, it is not supported by std::multimap
It depends on the implementation of std::multimap

Question 4

How can you retrieve all the elements with a given key in a std::multimap?

By calling the find() function multiple times until it returns an invalid iterator
By calling the search() function with the key as an argument
By calling the equal_range() function with the key as an argument
By calling the get() function with the key as an argument

Question 5

What is the return type of the equal_range() function in a std::multimap?

A boolean value indicating whether the element was found
A reference to the element
A pointer to the element
A pair of iterators to the first and last element with the given key

Question 6

How is the std::map class implemented in C++?

As a linked list
As an array
As a red-black tree
As a hash table

Question 7

What is the output of the following code?

C++

#include <iostream>
#include <map>

int main() {
    std::map<int, int> m {{1, 2}, {3, 4}, {5, 6}};  
    m[3] = 5;                                       
    for (auto it = m.begin(); it != m.end(); ++it) {
        std::cout << it->first << " " << it->second << std::endl;  
    }
    return 0;
}

1 2
3 5
5 6
1 2
3 4
5 6
1 2
4 5
5 6
1 4
3 5
5 6

Question 8

Which of the following statements about std::map in C++ STL is NOT true?

A map stores unique keys in sorted order
A map is implemented as a self-balancing Red-Black Tree
A map allows insertion and deletion of elements
A map provides constant time access to elements

Question 9

What is the time complexity of clearing all elements from a map in the STL?

O(1)
O(n)
O(log n)
O(n log n)

Question 10

What is the time complexity of erasing an element from a map in the STL?

O(1)
O(n)
O(log n)
O(n log n)

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C++

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