Character vs string comparison in C++ - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of character and string comparison

What is the output of this C++ code snippet?

C++

#include <iostream>
#include <string>

int main() {
    char c = 'a';
    std::string s = "a";
    if (c == s) {
        std::cout << "Equal" << std::endl;
    } else {
        std::cout << "Not Equal" << std::endl;
    }
    return 0;
}

A Compilation error

B Not Equal

C Equal

D Runtime error

💡 Hint

Think about the types being compared: char and std::string.

In C++, you cannot directly compare a char and a std::string using '=='. This causes a compilation error because the types are incompatible.

❓ Predict Output

intermediate

Comparing char with string using c_str()

What is the output of this C++ code?

C++

#include <iostream>
#include <string>
#include <cstring>

int main() {
    char c = 'a';
    std::string s = "a";
    if (std::strcmp(&c, s.c_str()) == 0) {
        std::cout << "Equal" << std::endl;
    } else {
        std::cout << "Not Equal" << std::endl;
    }
    return 0;
}

A Runtime error

B Not Equal

C Equal

D Compilation error

💡 Hint

Consider what &c points to and if it is a proper C-string.

The expression &c points to a single character, but it is not null-terminated. strcmp expects null-terminated strings, so this causes undefined behavior and likely a runtime error.

❓ Predict Output

advanced

Output of comparing char and string with explicit conversion

What is the output of this C++ code?

C++

#include <iostream>
#include <string>

int main() {
    char c = 'a';
    std::string s = "a";
    if (std::string(1, c) == s) {
        std::cout << "Equal" << std::endl;
    } else {
        std::cout << "Not Equal" << std::endl;
    }
    return 0;
}

A Not Equal

B Runtime error

C Compilation error

D Equal

💡 Hint

Look at how the char is converted to a string before comparison.

std::string(1, c) creates a string of length 1 containing the character c. Comparing this string to s which is "a" results in equality.

❓ Predict Output

advanced

Comparing char and string with operator== overload

What is the output of this C++ code?

C++

#include <iostream>
#include <string>

int main() {
    char c = 'a';
    std::string s = "a";
    if (c == s[0]) {
        std::cout << "Equal" << std::endl;
    } else {
        std::cout << "Not Equal" << std::endl;
    }
    return 0;
}

A Runtime error

B Equal

C Compilation error

D Not Equal

💡 Hint

Check what s[0] returns and how it compares to c.

s[0] returns a char, so comparing c and s[0] is a valid char-to-char comparison. Both are 'a', so output is "Equal".

🧠 Conceptual

expert

Why direct char and string comparison fails in C++

Why does the following code fail to compile in C++? char c = 'a'; std::string s = "a"; if (c == s) { // ... } Choose the best explanation.

A Because char variables cannot be used in if statements.

B Because std::string cannot be compared with any other type using operator==.

C Because char and std::string are different types and no operator== overload exists for comparing them directly.

D Because the compiler requires explicit casting of char to int before comparison.

💡 Hint

Think about type compatibility and operator overloading in C++.

C++ does not provide an operator== overload to compare a char directly with a std::string. They are different types, so the compiler cannot resolve the comparison.