Comparing Strings in C++: An Overview of 3 Methods

Discover in our latest blog post how to compare strings in C++ using three different methods. We'll show you how to use strcmp(), the built-in compare() function, and relational operators (==, !=). Find the best approach for your use case!

1. Using the String strcmp() function in C++

The C++ String class provides built-in functions for manipulating strings. The strcmp() function is a C library function used to compare two strings in a lexicographical manner.

strcmp() Syntax

The input string must be a char array of C-style String. strcmp() compares the strings in a case-sensitive form.

int strcmp(const char *str1, const char *str2);

This function returns the following values according to the matching cases:

• Returns 0 if both the strings are the same.
• Returns < 0 (less than zero) if the value of the character of the first string is smaller as compared to the second string input.
• Results out to be > 0 (greater than zero) when the second string is greater in comparison.

Example 1: Using strcmp()

#include 
#include 

int main() {
    const char *str_inp1 = "String Match";
    const char *str_inp2 = "String Unmatch";

    std::cout << "String 1: " << str_inp1 << std::endl;
    std::cout << "String 2: " << str_inp2 << std::endl;

    if (strcmp(str_inp1, str_inp2) == 0)
        std::cout << "\nBoth the input strings are equal." << std::endl;
    else
        std::cout << "\nThe input strings are not equal." << std::endl;
}

2. Using the compare() function in C++

C++ has a built-in compare() function to compare two strings.

compare() Syntax

int compare (const string& string-name) const;

This function returns the following values according to the matching cases:

• Returns 0 if both the strings are the same.
• Returns < 0 (less than zero) if the value of the character of the first string is smaller as compared to the second string input.
• Results out to be > 0 (greater than zero) when the second string is greater in comparison.

Example 1: Using compare()

#include 

int main() {
    std::string str_inp1("String Match");
    std::string str_inp2("String Match");

    std::cout << "String 1: " << str_inp1 << std::endl;
    std::cout << "String 2: " << str_inp2 << std::endl;

    int res = str_inp1.compare(str_inp2);

    if (res == 0)
        std::cout << "\nBoth the input strings are equal." << std::endl;
    else if (res < 0)
        std::cout << "\nString 1 is smaller as compared to String 2." << std::endl;
    else
        std::cout << "\nString 1 is greater as compared to String 2." << std::endl;
}

3. Relational Operators in C++

C++ Relational operators such as == (double equals) and != (not equals) can be helpful in the comparison of strings.

Relational Operators Syntax

string1 == string2

string1 != string2

Example 1: Using C++ == operator

#include 

int main() {
    std::string str_inp1;
    std::string str_inp2;

    std::cout << "Enter the String 1:\n"; std::cin >> str_inp1;
    std::cout << "Enter the String 2:\n"; std::cin >> str_inp2;

    if (str_inp1 == str_inp2)
        std::cout << "Strings are equal" << std::endl;
    else
        std::cout << "Strings are not equal" << std::endl;
}

Conclusion

In this article, you learned methods to compare strings in C++. This included String's strcmp() function, the built-in compare() function, and relational operators (==, !=). Continue your learning with more C++ tutorials.