Substring in C++ | Board Infinity

Introduction

You may use the substr() function to discover the substring inside a given string, or use a looping method to find the substring on your own. In this article, we'll go through a few methods for locating a string's substring given its length, beginning position, or ending position.

Syntax of the substr () function

A member method of the string class is called substr(). The syntax for the substr() function is as follows.

substr (pos, len)

A string object calls the substr() method.
Pos is the substring's beginning index or location within this string.
Len is the substring's length in characters.
Pos has a default value of zero.
The entire text is returned as a substring if pos is not supplied. Len can be omitted. The substring up until the end of this text is returned if len is not given.
A substring constructed using this string, pos, and len is represented by a freshly created string object that substr() returns.

Example #1:

Get a substring with a start point and length using substr(). In this example, we'll get a string with an initial value and look for the portion of it that begins at a specific position and ends at a particular length.

Code

#include <iostream>
using namespace std;

int main() {
string str1 = "We are changing the world.";

int pos = 5;
int len = 10;
string substring = str1.substr(pos, len);

cout << substring;
}

Output

e changing

write your code here: Coding Playground

Note: Len will be modified such that the substring terminates at the end of the main string even if you supply a length that exceeds the main string's maximum length.

Example #2:

Find Substring with just Start Position using substr() In this example, we'll take a text and search for the substring that begins at a specific beginning point. The length of the substring is not provided. The supplied start point through the string's conclusion should be covered by the returned substring.

Code

#include <iostream>
using namespace std;

int main() {
string str1 = "We are changing the world.";

int pos = 5;
string substring = str1.substr(pos);

cout << substring;
}

Output

e changing the world.

write your code here: Coding Playground

Example #3:

Finding a substring without any start point using substr() as an example In this illustration, we'll take a string with an initial value and identify its substring. The start location of the substring is not provided. The string that is given back must be a duplicate of the original string.

Code

#include <iostream>
using namespace std;

int main() {
string str1 = "We are changing the world.";

string substring = str1.substr();

cout << substring;
}

Output

We are changing the world.

write your code here: Coding Playground

Example #4:

Find Substring with End and Start Positions using substr() In this example, we'll take a string and search for the portion of it that starts at a specific starting position and ends at a specific finishing position. The length, not the end point, is the argument that the substr() method takes. As a result, we will modify the len input to create a length value by utilizing the start and end places of the original string's substring.

Code

#include <iostream>
using namespace std;

int main() {
string str1 = "We are changing the world.";

int start = 5;
int end = 12;
string substring = str1.substr(start, end - start + 1);

cout << substring;
}

Output

e changi

write your code here: Coding Playground

Example #5:

Using a for loop to find a substring In this example, we'll use a C++ For Loop to locate the substring of a text given its start position and length.

Code

#include <iostream>
using namespace std;

int main() {
string str1 = "We are changing the world.";

int start = 5;
int len = 10;

char substring[len+1];

for(int i=0; i < len; i++) {
substring[i] = str1[start + i];
}

substring[len] = '\0';

cout << substring;
}

Output

e changing

write your code here: Coding Playground

For the same purpose, you may discover the substring using a Do While or While loop in C++ as well.

Conclusion

This C++ tutorial showed us how to use example scripts to understand how to determine a string's substring in C++.