String Comparison

Part of the Fundamentals section of Coddy's C++ journey — lesson 22 of 74.

In C++, comparing strings can be done in multiple ways. Since std::string is a class, it has overloaded operators that make string comparison intuitive and straightforward.

The most common way to compare strings is using comparison operators (==, !=, <, >, <=, >=):

string str1 = "hello";
string str2 = "hello";
string str3 = "Hello";

bool result1 = (str1 == str2);  // true
bool result2 = (str1 == str3);  // false (case-sensitive)
bool result3 = (str1 != str3);  // true

You can also use the compare() method, which returns 0 if strings are equal, a negative integer if the first string is lexicographically smaller, and a positive integer if it's larger. Note that the exact value is implementation-defined — it is not necessarily -1 or 1:

string str1 = "a";
string str2 = "b";
string str3 = "c";

cout << str2.compare(str1) << endl; 
// Positive (b comes after a)

cout << str2.compare(str3) << endl;
// Negative (b comes before c)

cout << str2.compare(str2) << endl;
// 0 (equal strings)

Cheat sheet

In C++, you can compare strings using comparison operators or the compare() method.

Using comparison operators:

string str1 = "hello";
string str2 = "hello";
string str3 = "Hello";

bool result1 = (str1 == str2);  // true
bool result2 = (str1 == str3);  // false (case-sensitive)
bool result3 = (str1 != str3);  // true

Using the compare() method:

Returns 0 if strings are equal, <0 if first string is lexicographically smaller, >0 if larger:

string str1 = "a";
string str2 = "b";
string str3 = "c";

cout << str2.compare(str1) << endl; // Positive (b comes after a)
cout << str2.compare(str3) << endl; // Negative (b comes before c)
cout << str2.compare(str2) << endl; // 0 (equal strings)

Try it yourself

This lesson doesn't include a code challenge.