String input and output in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read a string from the user using std::cin.

C++

#include <iostream>
#include <string>

int main() {
    std::string name;
    std::cout << "Enter your name: ";
    std::cin [1] name;
    std::cout << "Hello, " << name << "!\n";
    return 0;
}

Drag options to blanks, or click blank then click option'

A>>

B<<

C==

D>>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using << instead of >> with std::cin causes a compilation error.

Using == is a comparison operator, not for input.

The operator >> is used with std::cin to read input into a variable.

2fill in blank

medium

Complete the code to read a full line of text (including spaces) into a string variable.

C++

#include <iostream>
#include <string>

int main() {
    std::string sentence;
    std::cout << "Enter a sentence: ";
    std::getline(std::cin, [1]);
    std::cout << "You wrote: " << sentence << "\n";
    return 0;
}

Drag options to blanks, or click blank then click option'

Ainput

Bsentence

Cline

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable name that is not declared causes a compilation error.

Using std::cin >> variable reads only until the first space.

The std::getline function reads a whole line into the string variable passed as the second argument.

3fill in blank

hard

Fix the error in the code to correctly output the string variable message.

C++

#include <iostream>
#include <string>

int main() {
    std::string message = "Welcome!";
    std::cout [1] message [2] std::endl;
    return 0;
}

Drag options to blanks, or click blank then click option'

A+

B>>

C<<

D=

Attempts:

3 left

💡 Hint

Common Mistakes

Using >> instead of << causes compilation errors.

Using + does not work with std::cout for output chaining.

To output text with std::cout, use the insertion operator <<.

4fill in blank

hard

Fill both blanks to create a dictionary (map) comprehension that stores word lengths for words longer than 3 characters.

C++

#include <iostream>
#include <string>
#include <map>
#include <vector>

int main() {
    std::vector<std::string> words = {"apple", "cat", "banana", "dog"};
    std::map<std::string, int> lengths;
    for (const auto& word : words) {
        if (word.[1]() > 3) {
            lengths[word] = word.[2]();
        }
    }
    for (const auto& [w, len] : lengths) {
        std::cout << w << ": " << len << "\n";
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Asize

Blength

Ccount

Dsize_t

Attempts:

3 left

💡 Hint

Common Mistakes

Using count() is incorrect because it does not exist for strings.

Using size_t is a type, not a method.

Use word.length() or word.size() to get the length of a string in C++. Both work, but here the first blank uses length() and the second uses size().

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths for words longer than 4 characters.

C++

#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <algorithm>

int main() {
    std::vector<std::string> words = {"apple", "cat", "banana", "dog", "elephant"};
    std::map<std::string, int> result;
    for (auto word : words) {
        if (word.[1]() > 4) {
            std::transform(word.begin(), word.end(), word.begin(), ::[2]);
            result[[3]] = word.size();
        }
    }
    for (const auto& [w, len] : result) {
        std::cout << w << ": " << len << "\n";
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Alength

Btoupper

Cword

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using size() instead of length() in the condition is acceptable but here only length() is correct.

Using tolower instead of toupper changes to lowercase.

The code checks if the word length is greater than 4 using length(). It converts the word to uppercase using toupper in std::transform. Finally, it uses the uppercase word as the key in the map.