How to split a string in C/C++, Python and Java?

08 Jul, 2022
Splitting a string by some delimiter is a very common task. For example, we have a comma-separated list of items from a file and we want individual items in an array. Almost all programming languages, provide a function split a string by some delimiter. 
// Splits str[] according to given delimiters.
// and returns next token. It needs to be called
// in a loop to get all tokens. It returns NULL
// when there are no more tokens.
char * strtok(char str[], const char *delims);
C
// A C/C++ program for splitting a string// using strtok()#include <stdio.h>#include <string.h> int main(){    char str[] = "Geeks-for-Geeks";     // Returns first token    char *token = strtok(str, "-");       // Keep printing tokens while one of the    // delimiters present in str[].    while (token != NULL)    {        printf("%s\n", token);        token = strtok(NULL, "-");    }     return 0;}
Output: Geeks
    for
    Geeks
Time complexity : O(n)
Auxiliary Space: O(n)
Note:  The main disadvantage of strtok() is that it only works for C style strings.
       Therefore we need to explicitly convert C++ string into a char array.
       Many programmers are unaware that C++ has two additional APIs which are more elegant
       and works with C++ string. 
Prerequisite:  stringstream API 
Stringstream object can be initialized using a string object, it automatically tokenizes strings on space char. Just like “cin” stream stringstream allows you to read a string as a stream of words.
Some of the Most Common used functions of StringStream.
clear() — flushes the stream 
str() —  converts a stream of words into a C++ string object.
operator << — pushes a string object into the stream.
operator >> — extracts a word from the stream.
 The code below demonstrates it. 
C++
#include <bits/stdc++.h>using namespace std; // A quick way to split strings separated via spaces.void simple_tokenizer(string s){    stringstream ss(s);    string word;    while (ss >> word) {        cout << word << endl;    }} int main(int argc, char const* argv[]){    string a = "How do you do!";    // Takes only space separated C++ strings.    simple_tokenizer(a);    cout << endl;    return 0;}
Output : How 
     do 
     you
     do!
Prerequisite: find function and substr().
This method is more robust and can parse a string with any delimiter, not just spaces(though the default behavior is to separate on spaces.) The logic is pretty simple to understand from the code below.
C++
#include <bits/stdc++.h>using namespace std; void tokenize(string s, string del = " "){    int start = 0;    int end = s.find(del);    while (end != -1) {        cout << s.substr(start, end - start) << endl;        start = end + del.size();        end = s.find(del, start);    }    cout << s.substr(start, end - start);}int main(int argc, char const* argv[]){    // Takes C++ string with any separator    string a = "Hi$%do$%you$%do$%!";    tokenize(a, "$%");    cout << endl;     return 0;}
Output: Hi 
    do 
    you
    do
    !
Method 3: Using  temporary string
If you are given that the length of the delimiter is 1, then you can simply use a temp string to split the string. This will save the function overhead time in the case of method 2.
C++
#include <iostream>using namespace std; void split(string str, char del){    // declaring temp string to store the curr "word" upto del      string temp = "";         for(int i=0; i<(int)str.size(); i++){        // If cur char is not del, then append it to the cur "word", otherwise          // you have completed the word, print it, and start a new word.         if(str[i] != del){            temp += str[i];        }          else{            cout << temp << " ";              temp = "";        }    }             cout << temp;} int main() {     string str = "geeks_for_geeks";    // string to be split     char del = '_';    // delimiter around which string is to be split         split(str, del);         return 0;}
geeks for geeks
Time complexity : O(n)
Auxiliary Space: O(n)
In Java : In Java, split() is a method in String class. 
// expregexp is the delimiting regular expression; 
// limit is the number of returned strings
public String[] split(String regexp, int limit);

// We can call split() without limit also
public String[] split(String regexp)
Java
// A Java program for splitting a string// using split()import java.io.*;public class Test{    public static void main(String args[])    {        String Str = new String("Geeks-for-Geeks");         // Split above string in at-most two strings         for (String val: Str.split("-", 2))            System.out.println(val);         System.out.println("");           // Splits Str into all possible tokens        for (String val: Str.split("-"))            System.out.println(val);    }}
Output: 
Geeks
for-Geeks

Geeks
for
Geeks
In Python: The split() method in Python returns a list of strings after breaking the given string by the specified separator.  
 
  // regexp is the delimiting regular expression; 
  // limit is limit the number of splits to be made 
  str.split(regexp = "", limit = string.count(str))  
Python3
line = "Geek1 \nGeek2 \nGeek3"print(line.split())print(line.split(' ', 1))
Output: 
['Geek1', 'Geek2', 'Geek3']
['Geek1', '\nGeek2 \nGeek3'] 
Python Programming Tutorial - Logical Operations and Splitting in Strings | GeeksforGeeks - YouTubeGeeksforGeeks532K subscribersPython Programming Tutorial - Logical Operations and Splitting in Strings | GeeksforGeeksWatch laterShareCopy linkInfoShoppingTap to unmuteIf playback doesn't begin shortly, try restarting your device.More videosMore videosYou're signed outVideos you watch may be added to the TV's watch history and influence TV recommendations. To avoid this, cancel and sign in to YouTube on your computer.CancelConfirmSwitch cameraShareInclude playlistAn error occurred while retrieving sharing information. Please try again later.Watch on0:000:000:00 / 4:31•Live•<div class="player-unavailable"><h1 class="message">An error occurred.</h1><div class="submessage"><a href="https://www.youtube.com/watch?v=m9iv9aM6Om8" target="_blank">Try watching this video on www.youtube.com</a>, or enable JavaScript if it is disabled in your browser.</div></div>
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