String handling basics in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of string concatenation and length

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

C++

#include <iostream>
#include <string>

int main() {
    std::string a = "Hello";
    std::string b = "World";
    std::string c = a + " " + b;
    std::cout << c << " " << c.length() << std::endl;
    return 0;
}

A Hello World 10

B HelloWorld 10

C Hello World 11

D HelloWorld 11

💡 Hint

Remember that adding a space between strings adds one character to the length.

The strings "Hello" and "World" are concatenated with a space in between, so the result is "Hello World" which has 11 characters including the space.

❓ Predict Output

intermediate

Output of string find method

What will this program print?

C++

#include <iostream>
#include <string>

int main() {
    std::string s = "programming";
    size_t pos = s.find("gram");
    std::cout << pos << std::endl;
    return 0;
}

A 3

B 0

C -1

D 7

💡 Hint

The find method returns the index where the substring starts.

The substring "gram" starts at index 3 in "programming" (p=0, r=1, o=2, g=3).

❓ Predict Output

advanced

Output of string substr and concatenation

What is the output of this code?

C++

#include <iostream>
#include <string>

int main() {
    std::string s = "abcdef";
    std::string t = s.substr(1, 3) + s.substr(4);
    std::cout << t << std::endl;
    return 0;
}

A bcdef

B fedcb

C cdef

D bcde

💡 Hint

Check carefully the substr parameters and concatenation.

s.substr(1,3) is "bcd" and s.substr(4) is "ef", concatenated gives "bcdef".

❓ Predict Output

advanced

Output of string comparison

What does this program print?

C++

#include <iostream>
#include <string>

int main() {
    std::string a = "apple";
    std::string b = "banana";
    if (a < b) {
        std::cout << "a < b" << std::endl;
    } else {
        std::cout << "a >= b" << std::endl;
    }
    return 0;
}

A Runtime error

B a >= b

C Compilation error

D a < b

💡 Hint

Strings are compared lexicographically (dictionary order).

"apple" is lexicographically less than "banana", so the output is "a < b".

❓ Predict Output

expert

Output of string erase and insert

What is the output of this program?

C++

#include <iostream>
#include <string>

int main() {
    std::string s = "hello world";
    s.erase(5, 1);
    s.insert(5, ",");
    std::cout << s << std::endl;
    return 0;
}

A hello world

B hello,world

C hello, world

D helloworld

💡 Hint

Erase removes the space, insert adds a comma at the same position.

The space at index 5 is erased, then a comma is inserted at index 5, resulting in "hello,world".