C++ Interview Questions and Answers - C Style Algorithms

This section on C++ interview questions and answers focuses on “C Style Algorithms”. One shall practice these interview questions to improve their C++ programming skills needed for various interviews (campus interviews, walkin interviews, company interviews), placements, entrance exams and other competitive exams. These questions can be attempted by anyone focusing on learning C++ programming language. They can be a beginner, fresher, engineering graduate or an experienced IT professional. Our C++ interview questions come with detailed explanation of the answers which helps in better understanding of C++ concepts.

Here is a listing of C++ interview questions on “C Style Algorithms” along with answers, explanations and/or solutions:

1. Pick out the in correct type of function in <algorithm> header file.
a) Partitions
b) Sort
c) Merge
d) Join
View Answer

Answer: d
Explanation: First three type of options are available in <algorithm> header file.

2. What type of algorithm is not available in creating our own STL style algorithms?
a) copy_if()
b) remove_copy_if()
c) sort
d) remove_copy()
View Answer

Answer: a
Explanation: copy_if() algorithm is not available in creating our own STL style algorithms.

3. What is meant by hash tables in C++?
a) Array data structure
b) Keyed array data structure
c) Data structure
d) Linear probing
View Answer

Answer: b
Explanation: In hash table, every value will have a key, So that it can be accessed easily.

4. What will be the output of the following C++ code?

```
    #include <iostream>
```
```
    #include <algorithm>
```
```
    #include <vector>
```
```
    using namespace std;
```
```
    int main ()  
```
```
    {
```

        int myints[] = {10, 20, 30, 5, 15};

        vector<int> v(myints, myints + 5);

```
        make_heap (v.begin(), v.end());
```
```
        pop_heap (v.begin(), v.end());
```
```
        v.pop_back();
```
```
        cout << v.front() << '\n';
```
```
        return 0;
```
```
    }
```

a) 10
b) 20
c) 30
d) 5
View Answer

Answer: b
Explanation: In this program, We are forming a heap with the vector and then we are popping one element and finding the maximum element in the heap.
Output:

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$ g++ style.cpp
$ a.out
20

5. What will be the output of the following C++ code?

```
    #include <iostream> 
```
```
    #include <algorithm>
```
```
    #include <vector>
```
```
    using namespace std;
```
```
    int main ()
```
```
    {
```

        int first[] = {5, 10, 15, 20, 25};

        int second[] = {50, 40, 30, 20, 10};

```
        vector<int> v(10);
```
```
        vector<int> :: iterator it;
```
```
        sort (first, first + 5);
```
```
        sort (second, second + 5);
```

        it = set_union (first, first + 5, second, second + 5, v.begin());

```
        v.resize(it-v.begin());
```

        for (it = v.begin(); it != v.end(); ++it)

```
            cout << ' ' << *it;
```
```
        cout << '\n';
```
```
        return 0;
```
```
    }
```

a) 5 10 15
b) 20 25 30
c) 40 50
d) 20 25
View Answer

Answer: d
Explanation: In this kind of style algorithm, We are finding the elements in the both the vector by using set_union function.
Output:

$ g++ style1.cpp
$ a.out
5 10 15 20 25 30 40 50

6. What will be the output of the following C++ code?

```
    #include <iostream>
```
```
    #include <algorithm>
```
```
    #include <vector>
```
```
    using namespace std;
```
```
    bool myfunction (int i, int j)
```
```
    { 
```
```
        return (i < j);
```
```
    }
```
```
    struct myclass {
```
```
    bool operator() (int i, int j)
```
```
    {
```
```
        return (i < j);
```
```
    } 
```
```
    } myobject;
```
```
    int main () 
```
```
    {
```
```
        int myints[] = {10, 9, 8};
```

        vector<int> myvector (myints, myints + 3);

        sort (myvector.begin(), myvector.begin() + 2);

        sort (myvector.begin() + 1, myvector.end(), myfunction);

        sort (myvector.begin(), myvector.end(), myobject);

        for (vector<int> :: iterator it = myvector.begin(); it != myvector.end(); ++it)

```
            cout << ' ' << *it;
```
```
        return 0;
```
```
    }
```

a) 8 9 10
b) 10 8 9
c) 9 8 10
d) 10 8 8
View Answer

Answer: a
Explanation: In this style algorithm, We have sorted the elements in the vector by using the sort method.
Output:

$ g++ style2.cpp
$ a.out
8 9 10

7. What will be the output of the following C++ code?

```
    #include <iostream>
```
```
    #include <algorithm>
```
```
    #include <vector>
```
```
    using namespace std;
```
```
    bool myfunction (int i,int j) 
```
```
    {
```
```
        return (i < j);
```
```
    }
```
```
    int main () 
```
```
    {
```
```
        int myints[] = {9, 8, 7, 6};
```

        vector<int> myvector (myints, myints + 4);

        partial_sort (myvector.begin(), myvector.begin() + 2, myvector.end());

        partial_sort (myvector.begin(), myvector.begin() + 2, myvector.end(),

```
        myfunction);
```

        for (vector<int> :: iterator it = myvector.begin(); it != myvector.end(); ++it)

```
            cout << ' ' << *it;
```
```
        return 0;
```
```
    }
```

a) 6 7 8 9
b) 9 8 6 7
c) 6 7 9 8
d) 9 8 5 7
View Answer

Answer: c
Explanation: In this program, We are partial sorting the vector by using the partial sort method.
Output:

$ g++ style3.cpp
$ a.out
6 7 9 8

8. What will be the output of the following C++ code?

```
    #include <iostream>
```
```
    #include <algorithm>
```
```
    #include <vector>
```
```
    using namespace std;
```
```
    int main () 
```
```
    {
```
```
        int first[] = {5, 10, 15};
```
```
        int second[] = {50, 40, 30};
```
```
        vector<int> v(4);
```
```
        vector<int> :: iterator it;
```
```
        sort (first, first + 3);
```
```
        sort (second, second + 3);
```

        it = set_symmetric_difference (first, first + 2, second, second + 2,

```
        v.begin());
```
```
        v.resize(it - v.begin());
```

        for (it = v.begin(); it != v.end(); ++it)

```
        cout << ' ' << *it;
```
```
        return 0;
```
```
    }
```

a) 5 10
b) 30 40
c) 50 40
d) 5 10 30 40
View Answer

Answer: d
Explanation: In this style algorithm, We are finding the symmetric difference between the vectors and printing it.
Output:

$ g++ style4.cpp
$ a.out
5 10 30 40

9. What is the use of includes function in c++?
a) Compares two ranges of data
b) Compares two sorted ranges of data
c) Includes a new element in the range
d) Includes a new element in the end
View Answer

Answer: b
Explanation: Returns true if the first sorted range contains all the elements in the second sorted range.

10. How many parameters are required for sort_heap function?
a) 1
b) 2
c) 2 or 3
d) 3
View Answer

Answer: c
Explanation: There are three parameters required for sort_heap. There are first element in heap and last element in heap and an optional compare.

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