C++ String Interview Questions and Answers

This set of C++ Programming Multiple Choice Questions & Answers (MCQs) focuses on “String – 2”.

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

#include <iostream> 
#include <string>
#include <cstring>
using namespace std; 
int main(int argc, char const *argv[])
{
	const char *a = "Hello\0World";
	cout<<a;
	return 0;
}

a) Hello World
b) Hello
c) World
d) Error
View Answer

Answer: b
Explanation: char* are terminated by a ‘\0’ character so the string “Hello\0World” will be cut down to “Hello”.

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

#include <iostream> 
#include <string>
#include <cstring>
using namespace std; 
int main(int argc, char const *argv[])
{
	string s("a");
	cout<<s;
	return 0;
}

a) a
b) empty string
c) Error
d) Segmentation fault
View Answer

Answer: a
Explanation: string class has a constructor for this call hence the string s will be assigned “a”.

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

#include <iostream> 
#include <string>
#include <cstring>
using namespace std; 
int main()
{
	string s('a');
	cout<<s;
	return 0;
}

a) a
b) empty string
c) Error
d) Segmentation fault
View Answer

Answer: c
Explanation: The string class provides string(string s) as a constructor not the string(char) as a constructor therefore this assignment is not valid.

4. Which is the correct way of concatenating a character at the end of a string object?

way 1:
string s;
s = s + 'a';
 
way 2:
string s;
s.push_back('a');

a) 1 only
b) 2 only
c) both of them
d) both are wrong
View Answer

Answer: c
Explanation: string class provides the addition of char and string and also push_back(char) function to append a character at the end of a string.

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

#include <iostream>
#include <string>
using namespace std;
int main ()
{
  std::string str ("Sanfoundry.");
  str.back() = '!';
  std::cout << str << endl;
  return 0;
}

a) Sanfoundry.!
b) Sanfoundry.
c) Sanfoundry!
d) Sanfoundry!.
View Answer

Answer: c
Explanation: back() function modifies the last character of the string with the character provided.

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

#include <iostream>
#include <string>
using namespace std;
int main ()
{
  string str ("sanfoundry.");
  str.front() = 'S';
  cout << str << endl;
  return 0;
}

a) Sanfoundry
b) Sanfoundry.
c) sanfoundry
d) sanfoundry.
View Answer

Answer: b
Explanation: front() modifies the first character of the string with the character provided.

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

#include <iostream>
#include <string>
using namespace std;
int main ()
{
  string str ("sanfoundry.");
  cout << str.substr(3).substr(4) << endl;
  return 0;
}

a) foundry.
b) dry.
c) oundry.
d) found
View Answer

Answer: b
Explanation: As we are first taking the substring of s from 3 to end then on that substring we are taking substr from 4 to end which is equal to “dry.”.

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

#include <iostream>
#include <string>
using namespace std;
int main ()
{
  string str = "Sanfoundry!";
  cout<<str.capacity();
  cout<<str.size();
  return 0;
}

a) 1511
b) 1111
c) 1115
d) 010
View Answer

Answer: a
Explanation: Capacity of a string object is defined as the length of string plus the extra space given to that object which will be used further if string is expanded.

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