How to Split strings in C++?

This topic will discuss how we can split given strings into a single word in the C++ programming language. When we divide a group of words or string collections into single words, it is termed the split or division of the string. However, splitting strings is only possible with some delimiters like white space ( ), comma (,), a hyphen (-), etc., making the words an individual. Furthermore, there is no predefined split function to divide the collection of strings into an individual string. So, here we will learn the different methods to split strings into a single one in C++.

Different method to achieve the splitting of strings in C++

Use strtok() function to split strings
Use custom split() function to split strings
Use std::getline() function to split string
Use find() and substr() function to split string

Use strtok() function to split strings

strtok(): A strtok() function is used to split the original string into pieces or tokens based on the delimiter passed.

Syntax

In the above syntax, a strtok() has two parameters, the str, and the delim.

str: A str is an original string from which strtok() function split strings.

delim: It is a character that is used to split a string. For example, comma (,), space ( ), hyphen (-), etc.

Return: It returns a pointer that references the next character tokens. Initially, it points to the first token of the strings.

Note: A strtok() function modifies the original string and puts a NULL character ('\0') on the delimiter position on each call of the strtok() function. In this way, it can easily track the status of the token.

Program to split strings using strtok() function

Let's consider an example to split string in C++ using strtok() function.

Program.cpp

#include <iostream>
#include <cstring>
using namespace std;

int main()
{
	char str[100]; // declare the size of string	
	cout << " Enter a string: " <<endl;
	cin.getline(str, 100); // use getline() function to read a string from input stream
	
	char *ptr; // declare a ptr pointer
	ptr = strtok(str, " , "); // use strtok() function to separate string using comma (,) delimiter.
	cout << " \n Split string using strtok() function: " << endl;
	// use while loop to check ptr is not null
	while (ptr != NULL)
	{
		cout << ptr  << endl; // print the string token
		ptr = strtok (NULL, " , ");
	}
	return 0;
}

Output

Enter a string:
Learn how to split a string in C++ using the strtok() function.

 Split string using strtok() function:
Learn
how
to
split
a
string
in
C++
Using
the
strtok()
function.

Program to use custom split() function to split strings

Let's write a program to split sequences of strings in C++ using a custom split() function.

Program2.cpp

#include <iostream>
#include <string>
#define max 8 // define the max string
using namespace std;

string strings[max]; // define max string

// length of the string
int len(string str)
{
	int length = 0;
	for (int i = 0; str[i] != '\0'; i++)
	{
		length++;
		
	}
	return length;   
}

// create custom split() function
void split (string str, char seperator)
{
	int currIndex = 0, i = 0;
	int startIndex = 0, endIndex = 0;
	while (i <= len(str))
	{
		if (str[i] == seperator || i == len(str))
		{
			endIndex = i;
			string subStr = "";
			subStr.append(str, startIndex, endIndex - startIndex);
			strings[currIndex] = subStr;
			currIndex += 1;
			startIndex = endIndex + 1;
		}
		i++;
		}	
}

int main()
{
	string str = "Program to split strings using custom split function.";
	char seperator = ' '; // space
	split(str, seperator);
	cout <<" The split string is: ";
	for (int i = 0; i < max; i++)
	{
		cout << "\n i : " << i << " " << strings[i];
	}
	return 0;
}

Output

The split string is:
 i : 0 Program
 i : 1 to
 i : 2 split
 i : 3 strings
 i : 4 using
 i : 5 custom
 i : 6 split
 i : 7 function.

Use std::getline() function to split string

A getline() function is a standard library function of C++ used to read the string from an input stream and put them into the vector string until delimiter characters are found. We can use std::getline() function by importing the <string> header file.

Syntax

It has three parameters:

str: A str is a variable that stores original string.

token: It stores the string tokens extracted from original string.

delim: It is a character that are used to split the string. For example, comma (,), space ( ), hyphen (-), etc.

Program to use getline() function to split strings

Let's consider an example to split strings using the getline() function in C++.

Program3.cpp

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
using namespace std;
 
int main()
{
    string S, T;  // declare string variables
 
    getline(cin, S); // use getline() function to read a line of string and store into S variable.
 
    stringstream X(S); // X is an object of stringstream that references the S string
 
 	// use while loop to check the getline() function condition
    while (getline(X, T, ' ')) {
    	/* X represents to read the string from stringstream, T use for store the token string and,
		 ' ' whitespace represents to split the string where whitespace is found. */
    	
        cout << T << endl; // print split string
    }
 
    return 0;
}

Output

Welcome to the JavaTpoint and Learn C++ Programming Language.
Welcome
to
the
JavaTpoint
and
Learn
C++
Programming
Language.

Program to split the given string using the getline() function

Let's consider an example to split a given string in C++ using the getline() function.

Program4.cpp

#include <iostream>
#include <string>
#include <vector>
#include <sstream>

void split_str( std::string const &str, const char delim,
		std::vector <std::string> &out )
		{
			// create a stream from the string
			std::stringstream s(str);
			
			std::string s2;
			while (std:: getline (s, s2, delim) )
			{
				out.push_back(s2); // store the string in s2
			}
		}
		
		int main()
		{
			std:: string s2 = "Learn How to split a string in C++";
			const char delim = ' '; /* define the delimiter like space (' '), comma (,), hyphen (-), etc. */
			
			std::cout << "Your given string is: " << s2;  
			std::vector <std::string> out; // store the string in vector
			split_str (s2, delim, out); // call function to split the string
			
			// use range based for loop
			for (const auto &s2: out)
			{
				std::cout << "\n" << s2;
			}
			return 0;
		}

Output

Your given string is: Learn How to split a string in C++
Learn
How
to
split
a
string
in
C++

Use find() and substr() function to split strings

Let's write a program to use find() function and substr() function to split given strings in C++.

Program4.cpp

#include <iostream>
#include <string>
using namespace std;
int main()
{
// given string with delimiter
string given_str = "How_to_split_a_string_using_find()_and_substr()_function_in_C++";
string delim = "_"; // delimiter

cout << " Your string with delimiter is: " << given_str << endl;
size_t pos = 0;
string token1; // define a string variable

// use find() function to get the position of the delimiters
while (( pos = given_str.find (delim)) != std::string::npos)
{
token1 = given_str.substr(0, pos); // store the substring 
cout << token1 << endl;
given_str.erase(0, pos + delim.length());  /* erase() function store the current positon and move to next token. */ 
}
cout << given_str << endl; // it print last token of the string.
}

Output

Your string with delimiter is: How_to_split_a_string_using_find()_and_substr()_function_in_C++
How
to
split
a
string
using
find()
and
substr()
function
in
C++

In the above program, we use a find() function inside the loop to repeatedly find the occurrence of the delimiter in the given string and then split it into tokens when the delimiter occurs. And the substr() function stores the sub-string to be printed. On the other hand, an erase() function stores the current position of the string and moves to the next token, and this process continues until we have got all the split strings.

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