A string is a collection of characters. For example, “neveropen” is a string. C++ provides primitive data types to create a string. The string can also be initialized at the time of declaration.
Syntax:
string str;
string str = “neveropen”
Here, “neveropen” is a string literal.
This article shows the difference between the concatenation of the strings using the addition assignment operator (+=) and the addition (+) operator used with strings. Concatenation is the process of joining end-to-end.
Addition assignment (+=) operator
In C++, a string addition assignment operator is used to concatenate one string to the end of another string.
Syntax:
str += value
Here,
value is a string to be concatenated with str.
It appends the value (literal) at the end of the string, without any reassignment.
Example: Below is the C++ program to demonstrate the addition assignment operator.
C++
// C++ program to implement// the above approach#include <iostream>using namespace std;// Driver codeint main(){ // Declaring an empty string string str = "Geeks"; // String to be concatenated string str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator str += str1; // Print the string cout << str; return 0;} |
Java
// Java program to implement// the above approachimport java.util.*;class GFG{// Driver codepublic static void main(String[] args){ // Declaring an empty String String str = "Geeks"; // String to be concatenated String str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator str += str1; // Print the String System.out.print(str);}}// This code is contributed by 29AjayKumar |
Python3
# Python code for the above approach # Driver code# Declaring an empty stringstr = "Geeks";# String to be concatenatedstr1 = "forGeeks";# Concatenate str and str1# using addition assignment operatorstr += str1;# Print the stringprint(str);# This code is contributed by gfgking |
C#
// C# program to implement// the above approachusing System;public class GFG{// Driver codepublic static void Main(String[] args){ // Declaring an empty String String str = "Geeks"; // String to be concatenated String str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator str += str1; // Print the String Console.Write(str);}}// This code is contributed by 29AjayKumar |
Javascript
<script> // JavaScript code for the above approach // Driver code // Declaring an empty string let str = "Geeks"; // String to be concatenated let str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator str += str1; // Print the string document.write(str); // This code is contributed by Potta Lokesh </script> |
Output
neveropen
Addition(+) operator
In C++, a string addition operator is used to concatenate one string to the end of another string. But in this case the after the concatenation of strings, the modified string gets assigned to the string.
Syntax:
str = str + value
Here,
value is a string to be concatenated with str.
It firstly appends the value (literal) at the end of the string and then reassigns it to str.
Example: Below is the C+ program to demonstrate the above approach.
C++
// C++ program to implement// the above approach#include <iostream>using namespace std;// Driver codeint main(){ // Declaring an empty string string str = "Geeks"; // String to be concatenated string str1 = "forGeeks"; // Concatenate str and str1 // using addition operator str = str + str1; // Print the string cout << str; return 0;} |
Java
// Java program to implement// the above approachclass GFG{// Driver codepublic static void main(String[] args){ // Declaring an empty String String str = "Geeks"; // String to be concatenated String str1 = "forGeeks"; // Concatenate str and str1 // using addition operator str = str + str1; // Print the String System.out.print(str);}}// This code is contributed by 29AjayKumar |
Python3
# Python program to implement# the above approach# Driver code# Declaring an empty stringstr1 = "Geeks"# String to be concatenatedstr2 = "forGeeks"# Concatenate str and str1# using addition operatorstr1 += str2# Print the stringprint(str1)# This code is contributed by phasing17 |
C#
// C# program to implement// the above approachusing System;public class GFG { // Driver code public static void Main(String[] args) { // Declaring an empty String String str = "Geeks"; // String to be concatenated String str1 = "forGeeks"; // Concatenate str and str1 // using addition operator str = str + str1; // Print the String Console.Write(str); }}// This code is contributed by umadevi9616 |
Javascript
// JavaScript program to implement// the above approach// Driver codefunction main() { // Declaring an empty string let str = "Geeks"; // String to be concatenated let str1 = "forGeeks"; // Concatenate str and str1 // using addition operator str = str + str1; // Print the string console.log(str);}main();// Contributed by adityashae15 |
Output
neveropen
Although both operators when used with strings can be used for the concatenation of strings, there are some differences between them:
Factor 1: Assignment of the modified string:
- The addition assignment operator (+=) concatenates two strings by appending one string at the end of another string.
- The addition operator(+) concatenates two strings by appending one string at the end of the original string and then assigning the modified string to the original string.
Example: Below is the C++ program to demonstrate the above approach.
C++
#include <iostream>using namespace std;int main(){ // Declaring an empty string string str = "Geeks"; // String to be concatenated string str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator // Concatenate str1 at the end of str str += str1; // Print the string cout << "Resultant string using += " << str << '\n'; str = "Geeks"; // Concatenate str and str1 // using addition operator // Concatenate str and str1 // and assign the result to str again str = str + str1; // Print the string cout << "Resultant string using + " << str; return 0;} |
Java
public class StringConcatenation { public static void main(String[] args) { // Declaring an empty string String str = "Geeks"; // String to be concatenated String str1 = "forGeeks"; // Concatenate str and str1 using += // Concatenate str1 at the end of str str += str1; // Print the string System.out.println("Resultant string using += " + str); // Reset str to its original value str = "Geeks"; // Concatenate str and str1 using + // Concatenate str and str1 // and assign the result to str again str = str + str1; // Print the string System.out.println("Resultant string using + " + str); }} |
Python3
# Python equivalent of above C++ code# Declaring an empty stringstr = "Geeks"# String to be concatenatedstr1 = "forGeeks"# Concatenate str and str1# using addition assignment operator# Concatenate str1 at the end of strstr += str1# Print the stringprint("Resultant string using += ",str)str = "Geeks"# Concatenate str and str1# using addition operator# Concatenate str and str1# and assign the result to str againstr = str + str1# Print the stringprint("Resultant string using + ",str) |
C#
using System;class Program { static void Main(string[] args) { // Declaring an empty string string str = "Geeks"; // String to be concatenated string str1 = "forGeeks"; // Concatenate str and str1 // using addition assignment operator // Concatenate str1 at the end of str str += str1; // Print the string Console.WriteLine("Resultant string using += " + str); // Reset str str = "Geeks"; // Concatenate str and str1 // using addition operator // Concatenate str and str1 // and assign the result to str again str = str + str1; // Print the string Console.WriteLine("Resultant string using + " + str); }} |
Javascript
// Declaring an empty stringlet str = "Geeks";// String to be concatenatedlet str1 = "forGeeks";// Concatenate str and str1 using +=// Concatenate str1 at the end of strstr += str1;// Print the stringconsole.log("Resultant string using += " + str);// Reset str to its original valuestr = "Geeks";// Concatenate str and str1 using +// Concatenate str and str1// and assign the result to str againstr = str + str1;// Print the stringconsole.log("Resultant string using + " + str); |
Output
Resultant string using += neveropen Resultant string using + neveropen
Factor 2: Operator overloaded functions used:
- The addition assignment operator (+=) concatenates two strings because the operator is overloaded internally.
- In this case, also, the addition operator (+) concatenates two strings because the operator is overloaded internally.
Factor 3: Number of strings concatenated:
- The addition assignment operator (+=) can concatenate two strings at a time in a single statement.
- The addition operator (+) can concatenate multiple strings by using multiple addition (+) operators between the string in a single statement. For example, str = str1 + str2 + str3 + … + strn
Example: In this program, three different statements are required to concatenate three strings; str, str1, str2, and str3 using the assignment addition operator (+=) and a single statement is required to concatenate three strings; str, str1, str2, and str3 using the addition operator (+).
C++
// C++ program to implement// the above approach#include <iostream>using namespace std;// Driver codeint main(){ // Declaring an empty string string str = "neveropen"; // String to be concatenated string str1 = " neveropen"; // String to be concatenated string str2 = " neveropen"; // String to be concatenated string str3 = " neveropen"; // Concatenate str, str1, str2 and str3 // using addition assignment operator // in multiple statements str += str1; str += str2; str += str3; // Print the string cout << "Resultant string using +=" << str << '\n'; str = "neveropen"; // Concatenate str, str1, str and str3 // using addition operator // in a single statement str = str + str1 + str2 + str3; // Print the string cout << "Resultant string using + " << str; return 0;} |
Java
// Java program to implement// the above approachimport java.io.*;class GFG {// Driver codepublic static void main (String[] args){ // Declaring an empty string String str = "neveropen"; // String to be concatenated String str1 = " neveropen"; // String to be concatenated String str2 = " neveropen"; // String to be concatenated String str3 = " neveropen"; // Concatenate str, str1, str2 and str3 // using addition assignment operator // in multiple statements str += str1; str += str2; str += str3; // Print the string System.out.println("Resultant string using +=" +str); str = "neveropen"; // Concatenate str, str1, str and str3 // using addition operator // in a single statement str = str + str1 + str2 + str3; // Print the string System.out.print("Resultant string using + " + str);}}//this code is contributed by shivanisinghss2110 |
Python3
# Initialize an empty stringstr = "neveropen"# Strings to be concatenatedstr1 = " neveropen"str2 = " neveropen"str3 = " neveropen"# Concatenate str, str1, str2, and str3# using the addition assignment operator# in multiple statementsstr += str1str += str2str += str3# Print the resultant stringprint("Resultant string using +=", str)# Reset the string to the original valuestr = "neveropen"# Concatenate str, str1, str2, and str3# using the addition operator in a single statementstr = str + str1 + str2 + str3# Print the resultant stringprint("Resultant string using +", str) |
C#
using System;class Program{ static void Main(string[] args) { // Declaring an empty string string str = "neveropen"; // Strings to be concatenated string str1 = " neveropen"; string str2 = " neveropen"; string str3 = " neveropen"; // Concatenate str, str1, str2, and str3 // using addition assignment operator // in multiple statements str += str1; str += str2; str += str3; // Print the string Console.WriteLine("Resultant string using +=" + str); // Reset the string str = "neveropen"; // Concatenate str, str1, str2, and str3 // using addition operator in a single statement str = str + str1 + str2 + str3; // Print the string Console.WriteLine("Resultant string using + " + str); }} |
Output
Resultant string using +=neveropen neveropen neveropen neveropen Resultant string using + neveropen neveropen neveropen neveropen
Factor 4: Performance:
- The addition assignment operator (+=) when used for the concatenation of strings gives better efficiency as compared to the addition(+) operator. This is because no reassignment of strings takes place in this case.
- The addition operator (+) when used for the concatenation of strings, is less efficient as compared to the addition (+=) operator. This is because the assignment of strings takes place in this case.
Example: Below is the program to demonstrate the performance of the += string concatenation method.
C++
// C++ program to calculate// performance of +=#include <bits/stdc++.h>#include <sys/time.h>using namespace std;// Function whose time is to// be measuredvoid fun(){ // Initialize a n empty string string str = ""; // concatenate the characters // from 'a' to 'z' for (int i = 0; i < 26; i++) { char c = 'a' + i; str += c; }}// Driver Codeint main(){ // Use function gettimeofday() // can get the time struct timeval start, end; // Start timer gettimeofday(&start, NULL); // unsync the I/O of C and C++. ios_base::sync_with_stdio(false); // Function Call fun(); // Stop timer gettimeofday(&end, NULL); // Calculating total time taken // by the program. double time_taken; time_taken = (end.tv_sec - start.tv_sec) * 1e6; time_taken = (time_taken + (end.tv_usec - start.tv_usec)) * 1e-6; cout << "Time taken by program is : " << fixed << time_taken << setprecision(6); cout << " sec" << endl; return 0;} |
Output
Time taken by program is : 0.000046 sec
Example: Below is the program to demonstrate the performance of the + string concatenation method.
C++
// C++ program to calculate// performance of +#include <bits/stdc++.h>#include <sys/time.h>using namespace std;// Function whose time is to// be measuredvoid fun(){ // Initialize a n empty string string str = ""; // concatenate the characters // from 'a' to 'z' for (int i = 0; i < 26; i++) { char c = 'a' + i; str = str + c; }}// Driver Codeint main(){ // Use function gettimeofday() // can get the time struct timeval start, end; // Start timer gettimeofday(&start, NULL); // unsync the I/O of C and C++. ios_base::sync_with_stdio(false); // Function Call fun(); // Stop timer gettimeofday(&end, NULL); // Calculating total time taken // by the program. double time_taken; time_taken = (end.tv_sec - start.tv_sec) * 1e6; time_taken = (time_taken + (end.tv_usec - start.tv_usec)) * 1e-6; cout << "Time taken by program is : " << fixed << time_taken << setprecision(6); cout << " sec" << endl; return 0;} |
Output
Time taken by program is : 0.000034 sec
| S No. | Factor | += operator | + operator |
| 1 | Assignment | It appends a string at the end of the original string. | It appends a string at the end of the original string and then reassigns the modified string to the original string. |
| 2 | Overloaded functions | operator overloaded function used with strings is different from the += operator. | operator overloaded function used with strings is different from the + operator. |
| 3 | Number of strings concatenated | It can concatenate two strings at a time in a single statement. | Multiple strings can be concatenated using multiple addition (+) operators between the string. For example, str = str1 + str2 + str3 + … + strn |
| 4 | Performance | This operator when used for the concatenation of strings gives better efficiency as compared to the addition(+) operator. This is because no reassignment of strings takes place in this case. | This operator when used for the concatenation is not as efficient as compared to the addition(+=) operator. This is because reassignment of strings takes place in this case. |
Feeling lost in the world of random DSA topics, wasting time without progress? It’s time for a change! Join our DSA course, where we’ll guide you on an exciting journey to master DSA efficiently and on schedule.
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 neveropen!
Ready to dive in? Explore our Free Demo Content and join our DSA course, trusted by over 100,000 neveropen!
