Different Ways to Compare Strings in C++

This section will discuss the different ways to compare the given strings in the C++ programming language. The comparison of the string determines whether the first string is equal to another string or not. Example: HELLO and Hello are two different strings.

There are different ways to compare the strings in the C++ programming language, as follows:

Using strcmp() function
Using compare() function
Using Relational Operator
Using For loop and If statement
Using user-defined function

strcmp() function

The strcmp() is a pre-defined library function of the string.h header file. The strcmp() function compares two strings on a lexicographical basis. This means that the strcmp() function starts comparing the first string with the second string, character by character until all characters in both strings are the same or a NULL character is encountered.

Syntax

Parameters:

leftstr: It defines the characters of the left string.

rightstr: It defines the characters of the right string.

Returns:

The leftstr string compares each character with the second string from the left side till the end of both strings. And, if both the strings are equal, the strcmp() function returns strings are equal. Else, the strings are not equal.

Let’s create a program to compare strings using the strcmp() function in C++.

Program1.cpp

  #include   using namespace std;  #include     int main ()  {  // declare strings  const char *str1 = ” Welcome to Tutor Aspire”;  const char *str2 = ” Welcome to Tutor Aspire”;    const char *str3 = ” tutoraspire”;  const char *str4 = ” tutoraspire”;    cout << ” String 1: ” << str1 << endl;  cout << ” String 2: ” << str2 << endl;    // use strcmp() function to validate the strings are equal  if (strcmp (str1, str2) == 0)  {  cout << ” n Both strings are equal. ” << endl;  }  else   {    cout << ” The strings are not equal. ” << endl;  }    cout << ” n String 3: ” << str3 << endl;  cout << ” String 4: ” << str4 << endl;    // use strcmp() function to validate the strings are equal  if (strcmp (str3, str4) == 0)  {  cout << ” n Both strings are equal. ” << endl;  }  else   cout << ” n The strings are not equal. “;    return 0;  }  

Output

 String 1:  Welcome to Tutor Aspire   String 2:  Welcome to Tutor Aspire     Both strings are equal.     String 3:  tutoraspire   String 4:  tutoraspire     The strings are not equal.

compare() function

The compare() function is a pre-defined library function of the C++ language. The compare() function compares two given strings and returns the following results based on the matching cases:

If both the strings are the same, the function returns 0.
If the character value of the first string is smaller than the second string, the function returns < 0.
If the second string is greater than the first string, the function returns greater than 0 or >0.

Syntax

Let’s create a simple program to compare two strings using the compare() function in C++.

Program2.cpp

  #include   using namespace std;  int main ()  {  string str1, str2; // declare string variable    cout << ” Enter the string 1: “;  cin >> str1;     cout << ” Enter the string 2: “;  cin >> str2;     // use compare() function to compare the second string with first string    int i = str1.compare(str2);    if ( i < 0)  {  cout << str1 << ” is smaller than ” << str2 << ” string” << endl;  }    else if ( i > 0)  {  cout << str2 << ” is greater than ” << str1 << ” string.” << endl;  }  else // i == 0;  {  cout << ” Both strings are equal.”;  }  return 0;  }  

Output

1st Run:  Enter the string 1: Program   Enter the string 2: program  Program is smaller than program string      2nd Run:  Enter the string 1: APPLE   Enter the string 2: APPLE   Both strings are equal.

Relational Operator

It is the operator used to compare two strings or numerical values in C++. C++ has different types of relational operators such as ‘==’, ‘!=’, >, < operator. But here, we use only two operators such as ‘==’ equal to and ‘!=’ not equal to a relational operator to compare the string easily.

Syntax

  String1 == string2  // here, we use double equal to operator  Or   String1 != string2 // here, we use not equal to operator  

Compare two strings using the Equal to (==) operator in C++

Equal To (==) operator: It is used to check the equality of the first string with the second string.

Let’s create a program to compare strings using the double equal to (==) operator in C++.

Program3.cpp

  #include   using namespace std;    int main ()  {  // declare string variables  string str1;  string str2;    cout << ” Enter the String 1: ” << endl;  cin >> str1;  cout << ” Enter the String 2: ” << endl;  cin >> str2;    // use ‘==’ equal to operator to check the equality of the string  if ( str1 == str2)  {  cout << ” String is equal.” << endl;  }  else  {  cout << ” String is not equal.” << endl;  }  return 0;  }  

Output

Enter the String 1:  tutoraspire   Enter the String 2:  tutoraspire   String is not equal.

2^nd Execution:

Enter the String 1:  Program   Enter the String 2:  Program   String is equal.

Compare two strings using the Not Equal To (!=) Relational Operator

Let’s create a program to compare whether the strings are equal or not using the Not Equal To (!=) operator in C++.

Program4.cpp

  #include   using namespace std;    int main ()  {  // declare string variables  string str1;  string str2;    cout << ” Enter the String 1: ” << endl;  cin >> str1;  cout << ” Enter the String 2: ” << endl;  cin >> str2;    // use ‘!=’ not equal to operator to check the equality of the string  if ( str1 != str2)  {  cout << ” String is not equal.” << endl;  }  else  {  cout << ” String is equal.” << endl;  }  return 0;  }  

Output

Enter the String 1:  tutoraspire   Enter the String 2:  tutoraspire   String is not equal.

2^nd Run:

Enter the String 1:  HELLO   Enter the String 2:  HELLO   String is equal.

Compare two strings using for loop and if statement in C++

Program5.cpp

  #include   using namespace std;  int main ()  {  char s1[50], s2[50]; // declare character array  int i, disp;    cout << ” Enter the String 1: ” << endl;  cin >> s1;    cout << ” Enter the String 2: ” << endl;  cin >> s2;    for (i = 0; s1[i] == s2[i] && s1[i] == ‘

Different Ways to Compare Strings in C++

Different Ways to Compare Strings in C++

strcmp() function

compare() function

Relational Operator

Compare two strings using the Equal to (==) operator in C++

Compare two strings using the Not Equal To (!=) Relational Operator

Compare two strings using for loop and if statement in C++

C++ try-catch

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