C++ program to compare two Strings using Operator Overloading

Pre-requisite: Operator Overloading in C++
Given two strings, how to check if the two strings are equal or not, using Operator Overloading.

Examples:

Input: ABCD, XYZ
Output: ABCD is not equal to XYZ
        ABCD is greater than XYZ

Input: Geeks, Geeks
Output: Geeks is equal to Geeks

Approach: Using binary operator overloading. 

• Declare a class with a string variable and operator function ‘==’, ‘<=’ and ‘>=’ that accepts an instance of the class and compares it’s variable with the string variable of the current instance.
• Create two instances of the class and initialize their class variables with the two input strings respectively.
• Now, use the overloaded operator(==, <= and >=) function to compare the class variable of the two instances.

Below is the implementation of the above approach: 

C++

// C++ program to compare two Strings
// using Operator Overloading

#include <cstring>
#include <iostream>
#include <string.h>

using namespace std;

// Class to implement operator overloading
// function for concatenating the strings
class CompareString {

public:
    // Classes object of string
    char str[25];

    // Parameterized Constructor
    CompareString(char str1[])
    {
        // Initialize the string to class object
        strcpy(this->str, str1);
    }

    // Overloading '==' under a function
    // which returns integer 1/true
    // if left operand string
    // and right operand string are equal.
    //(else return 0/false)
    int operator==(CompareString s2)
    {
        if (strcmp(str, s2.str) == 0)
            return 1;
        else
            return 0;
    }

    // Overloading '<=' under a function
    // which returns integer 1/true
    // if left operand string is smaller than
    // or equal to the right operand string.
    // (else return 0/false)
    int operator<=(CompareString s3)
    {
        if (strlen(str) <= strlen(s3.str))
            return 1;
        else
            return 0;
    }

    // Overloading '>=' under a function
    // which returns integer 1/true
    // if left operand string is larger than
    // or equal to the right operand string.
    //(else return 0/false)
    int operator>=(CompareString s3)
    {
        if (strlen(str) >= strlen(s3.str))
            return 1;
        else
            return 0;
    }
};

void compare(CompareString s1, CompareString s2)
{

    if (s1 == s2)
        cout << s1.str << " is equal to "
             << s2.str << endl;
    else {
        cout << s1.str << " is not equal to "
             << s2.str << endl;
        if (s1 >= s2)
            cout << s1.str << " is greater than "
                 << s2.str << endl;
        else
            cout << s2.str << " is greater than "
                 << s1.str << endl;
    }
}

// Testcase1
void testcase1()
{
    // Declaring two strings
    char str1[] = "Geeks";
    char str2[] = "ForGeeks";

    // Declaring and initializing the class
    // with above two strings
    CompareString s1(str1);
    CompareString s2(str2);

    cout << "Comparing \"" << s1.str << "\" and \""
         << s2.str << "\"" << endl;

    compare(s1, s2);
}

// Testcase2
void testcase2()
{
    // Declaring two strings
    char str1[] = "Geeks";
    char str2[] = "Geeks";

    // Declaring and initializing the class
    // with above two strings
    CompareString s1(str1);
    CompareString s2(str2);

    cout << "\n\nComparing \"" << s1.str << "\" and \""
         << s2.str << "\"" << endl;

    compare(s1, s2);
}

// Driver code
int main()
{
    testcase1();
    testcase2();

    return 0;
}

Output:

Comparing "Geeks" and "ForGeeks"
Geeks is not equal to ForGeeks
ForGeeks is greater than Geeks


Comparing "Geeks" and "Geeks"
Geeks is equal to Geeks