C++ Strings

Other Ways to Define a String in C++

In C++, strings can be defined using the following methods:

1. Using the std::string class:
The std::string class from the <string> header provides dynamic string manipulation.

string str = "Hello, World!";

2. Using character arrays:
Character arrays provide static string definition, but are less flexible than std::string.

char str[] = "Hello, World!";

3. Using pointers:
Strings can also be defined as pointers to character literals.

const char* str = "Hello, World!";

How to Take String Input in C++ with Examples?

Example 1: Single-word input using cin

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C++

#include <iostream>
using namespace std;

int main() {
    string word;
    cout << "Enter a word: ";
    cin >> word;
    cout << "You entered: " << word << endl;
    return 0;
}

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Example 2: Multi-word input using getline()

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C++

#include <iostream>
using namespace std;

int main() {
    string sentence;
    cout << "Enter a sentence: ";
    getline(cin, sentence);
    cout << "You entered: " << sentence << endl;
    return 0;
}

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How to Pass Strings to Functions?

Strings in C++ can be passed to functions in several ways:

1. Pass by value:
A copy of the string is passed, and changes in the function do not affect the original string.

void printString(string str) {
    cout << "String: " << str << endl;
}

2. Pass by reference:
The original string is passed, allowing modifications.

void modifyString(string &str) {
    str += " World!";
}

3. Pass by pointer:
A pointer to the string is passed, allowing modifications.

void printString(const string* str) {
    cout << "String: " << *str << endl;
}

Pointers and Strings

Pointers can be used to handle strings in C++. A pointer can reference a string literal or a dynamic string.

1. Pointer to a character array:

const char* str = "Hello";
cout << str;

2. Pointer to a dynamic string:

string* ptr = new string("Dynamic String");
cout << *ptr;
delete ptr;  // Free memory

Pointers enable efficient string manipulation but require careful memory management.

Difference between String and Character Array in C++

Common String Functions in C++:

• strlen(str1): It is used to find the length of a string.
• strcpy(str1,str2): It is used to copy the content of a string into another.
• strcat(str1,str2): It is used to append two strings.
• strcmp(str1,str2): this string function returns negative value if str1 is less than str2, 0 if str1 is equal to str2, and positive value if str1 is greater than str2.
• substr(starting index, from that index how many characters you want): It is used to take the substring from the given string.
   

Now we will discuss how to use the string function in C++ with the help of some examples.

String length example in C++

Here is a simple example of finding the string length using strlen(),size() and length() functions.

Code

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C++

// C++ Program to demonstrate the working of strlen(), size() and length()
#include<iostream>
#include<string.h>  // for string class
using namespace std;
int main()
{
    // Initializing the string
    char str1[]="codingninjas";
    string str2="string functions are very useful";
    cout<<"The length of the first string using strlen(): ";
    cout<<strlen(str1)<<endl;
    cout<<"The length of the second string using size(): ";
    cout<<str2.size()<<endl;
    cout<<"The length of the second string using length(): ";
    cout<<str2.length()<<endl;
    return 0;
}

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Output 

The length of the first string using strlen(): 12
The length of the second string using size(): 32
The length of the second string using length(): 32

String Copy Example in C++

Here is a simple example of copying the string using strcpy() function.

Code 

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C++

// Simple C++ Program to demonstrate the working of strcpy()
#include<iostream>
#include<string.h>  // for string class
using namespace std;
int main()
{
    // Initializing the string
    char str1[50]="Coding Ninjas";
    char str2[50];
    strcpy(str2,str1);
    cout<<"The value of the first string is: ";
    cout<<str1<<endl;
    cout<<"The value of the second string is: ";
    cout<<str2<<endl;
    return 0;
}

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Output 

The value of the first string is: Coding Ninjas
The value of the second string is: Coding Ninjas

String Concat Example in C++

Here is a simple example of the string concatenation using Strcat() function

Code 

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C++

// C++ Program to demonstrate the working of strcat()
#include<iostream>
#include<string.h>  // for string class
using namespace std;
int main()
{
    // Initializing the string
    char str1[]="Coding";
    char str2[]=" Ninjas";
    strcat(str1,str2);
    cout<<"The value of the first string is: ";
    cout<<str1<<endl;
    cout<<"The value of the second string is:";
    cout<<str2<<endl;
    return 0;
}

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Output

The value of the first string is: Coding Ninjas
The value of the second string is: Ninjas

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String Compare Example in C++

Here is a simple example of the string comparison using strcmp() function.

Code

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C++

// C++ Program to demonstrate the working of strcmp()
#include<iostream>
#include<string.h>  // for string class
using namespace std;
int main()
{
    // Initializing the string
    char str1[]="Coding";
    char str2[]="Coding";
    int res=strcmp(str1,str2);
    cout<<res<<endl;
    return 0;
}

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Output

0

In the above code, the res is 0. This means that both the strings are the same.

C++ String Functions

Here is a list of the string functions with their use.

Also check out - Substr C++

Frequently asked questions

What are the string functions in C++?

String functions are nothing, just functions that are used to perform operations on a string.

Which string function is used for the concatenation of two strings?

strcat(str1, str2) function is used to concatenate two strings.

Which header file is required for string functions in C++?

<string.h> is the header file required for string functions in C++.

Conclusion

Strings in C++ offer flexibility and versatility, making them essential for handling textual data in programs. With options like the dynamic std::string class and static character arrays, developers can choose the approach that best suits their needs. Whether taking input, passing strings to functions, or working with pointers, C++ provides robust tools for string manipulation. Understanding the differences and use cases of std::string and character arrays ensures better performance and more maintainable code.

You can learn more about such programming concepts here.

Recommended problems -

• Find the Shortest Substring in a String
• Subsequence of a String
• Beautiful String

This blog is over, but learning never stops, and there is a lot more to learn. Have a nice day and Happy Coding!