All substrings of a given String

Last Updated : 14 Feb, 2025
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Given a string s, containing lowercase alphabetical characters. The task is to print all non-empty substrings of the given string.

Examples : 

Input : s = "abc"
Output : "a", "ab", "abc", "b", "bc", "c"

Input : s = "ab"
Output : "a", "ab", "b"

Input : s = "a"
Output : "a"

[Expected Approach] - Using Iteration

  • The idea is to use two nested loops.
  • The outer loop picks the starting index (loop for i from 0 to n-1)
  • The inner loop picks the ending ending index (loop for j to n-1)
C++ 
// C++ program to find all the
// substrings of given string
#include <bits/stdc++.h>
using namespace std;

// Function to find all substrings
vector<string> findSubstrings(string &s) {

    // to store all substrings
    vector<string> res;

    for(int i = 0; i < s.length(); i++) {
        for(int j = i; j < s.length(); j++) {
            
            // substr function takes starting index
            // and length as parameters
            res.push_back(s.substr(i, j-i+1));
        }
    }

    return res;
}

int main() {
    string s = "abc";
    vector<string> res = findSubstrings(s);
    for(auto i:res) {
        cout<< i <<" ";
    }
    return 0;
}
C 
#include <stdio.h>
#include <string.h>

// Function to find all substrings
void findSubstrings(char *s) {
    
    // to store all substrings
    int len = strlen(s);
    for (int i = 0; i < len; i++) {
        for (int j = i; j < len; j++) {
            for (int k = i; k <= j; k++) {
                putchar(s[k]);
            }
            printf(" ");
        }
    }
}

int main() {
    char s[] = "abc";
    findSubstrings(s);
    return 0;
}
Java 
// Function to find all substrings
import java.util.ArrayList;
import java.util.List;

public class Main {
    public static List<String> findSubstrings(String s) {
        
        // to store all substrings
        List<String> res = new ArrayList<>();
        for (int i = 0; i < s.length(); i++) {
            for (int j = i; j < s.length(); j++) {
                
                // substr function takes starting index
                // and ending index + 1 as parameters
                res.add(s.substring(i, j + 1));
            }
        }
        return res;
    }

    public static void main(String[] args) {
        String s = "abc";
        List<String> res = findSubstrings(s);
        for (String i : res) {
            System.out.print(i + " ");
        }
    }
}
Python 
# Function to find all substrings
def find_substrings(s):
    
    # to store all substrings
    res = []
    for i in range(len(s)):
        for j in range(i, len(s)):
            res.append(s[i:j+1])
    return res

s = 'abc'
res = find_substrings(s)
for i in res:
    print(i, end=' ')
C# 
// Function to find all substrings
using System;
using System.Collections.Generic;

class Program {
    public static List<string> FindSubstrings(string s) {
        
        List<string> res = new List<string>();
        
        for (int i = 0; i < s.Length; i++) {
            for (int j = i; j < s.Length; j++) {
                
                // substr function takes starting index
                // and length as parameters
                res.Add(s.Substring(i, j - i + 1));
            }
        }
        return res;
    }

    static void Main() {
        string s = "abc";
        List<string> res = FindSubstrings(s);
        foreach (var i in res) {
            Console.Write(i + " ");
        }
    }
}
JavaScript 
// Function to find all substrings
function findSubstrings(s) {
    
    // to store all substrings
    let res = [];
    for (let i = 0; i < s.length; i++) {
        for (let j = i; j < s.length; j++) {
            
            // substr function takes starting index
            // and ending index + 1 as parameters
            res.push(s.substring(i, j + 1));
        }
    }
    return res;
}

let s = 'abc';
let res = findSubstrings(s);
res.forEach(i => {
    process.stdout.write(i + ' ');
});

Output
a ab abc b bc c

[Interesting Approach] - Using Recursion

The idea is to recursively generate all possible substrings of the given string s. To do so, create an array of string res[] to store the substrings of string s and an empty string cur to store the current string. Start from the 0th index and for each index ind, add the current character s[ind] in the string cur, and add the string cur in res[]. Then, move to index ind + 1, and recursively generate the all substrings. At each recursive call, check if string cur is empty, if so, skip the current character to start the string from next index ind + 1. At last print all the substrings.

C++ 
// C++ program to find all the
// substrings of given string
#include <bits/stdc++.h>
using namespace std;

// Recursive Function to find all
// substrings of a string
void subString(string &s, int n, int index, 
            string &cur, vector<string> &res) {

    // if we have reached the 
    // end of the string
    if (index == n) {
        return;
    }

    // add the character s[index] 
    // to the current string
    cur.push_back(s[index]);

    // add the current string in result
    res.push_back(cur);

    // move to next index
    subString(s, n, index + 1, cur, res);

    // remove the current character
    // from the current string 
    cur.pop_back();

    
    // if current string is empty
    // skip the current index to
    // start the new substring
    if(cur.empty()) {
        subString(s, n, index + 1, cur, res);
    }
}

// Function to find all substrings
vector<string> findSubstrings(string s) {

    // to store all substrings
    vector<string> res;
    
    // to store current string
    string cur = "";
    subString(s, s.length(), 0, cur, res);
    return res;
}

int main() {
    string s = "abc";
    vector<string> res = findSubstrings(s);
    for(auto i:res) {
        cout<< i <<" ";
    }
    return 0;
}
Java 
// Java program to find all the
// substrings of given string
import java.util.*;

class GFG {

    // Recursive Function to find all
    // substrings of a string
    static void subString(String s, int n, int index,
                          StringBuilder cur, List<String> res) {

        // if we have reached the
        // end of the string
        if (index == n) {
            return;
        }

        // add the character s.charAt(index)
        // to the current string
        cur.append(s.charAt(index));

        // add the current string in result
        res.add(cur.toString());

        // move to next index
        subString(s, n, index + 1, cur, res);

        // remove the current character
        // from the current string
        cur.deleteCharAt(cur.length() - 1);

        // if current string is empty
        // skip the current index to
        // start the new substring
        if (cur.length() == 0) {
            subString(s, n, index + 1, cur, res);
        }
    }

    // Function to find all substrings
    static List<String> findSubstrings(String s) {

        // to store all substrings
        List<String> res = new ArrayList<>();

        // to store current string
        StringBuilder cur = new StringBuilder();
        subString(s, s.length(), 0, cur, res);
        return res;
    }

    public static void main(String[] args) {
        String s = "abc";
        List<String> res = findSubstrings(s);
        for (String str : res) {
            System.out.print(str + " ");
        }
    }
}
Python 
# Python program to find all the
# substrings of given string

# Recursive Function to find all
# substrings of a string
def subString(s, n, index, cur, res):

    # if we have reached the
    # end of the string
    if index == n:
        return

    # add the character s[index]
    # to the current string
    cur += s[index]

    # add the current string in result
    res.append(cur)

    # move to next index
    subString(s, n, index + 1, cur, res)

    # remove the current character
    # from the current string
    cur = cur[:-1]

    # if current string is empty
    # skip the current index to
    # start the new substring
    if not cur:
        subString(s, n, index + 1, cur, res)

# Function to find all substrings
def findSubstrings(s):

    # to store all substrings
    res = []

    # to store current string
    cur = ""
    subString(s, len(s), 0, cur, res)
    return res

if __name__ == "__main__":
    s = "abc"
    res = findSubstrings(s)
    print(" ".join(res))
C# 
// C# program to find all the
// substrings of given string
using System;
using System.Collections.Generic;

class GFG {

    // Recursive Function to find all
    // substrings of a string
    static void subString(string s, int n, int index,
                          List<char> cur, List<string> res) {

        // if we have reached the
        // end of the string
        if (index == n) {
            return;
        }

        // add the character s[index]
        // to the current string
        cur.Add(s[index]);

        // add the current string in result
        res.Add(new string(cur.ToArray()));

        // move to next index
        subString(s, n, index + 1, cur, res);

        // remove the current character
        // from the current string
        cur.RemoveAt(cur.Count - 1);

        // if current string is empty
        // skip the current index to
        // start the new substring
        if (cur.Count == 0) {
            subString(s, n, index + 1, cur, res);
        }
    }

    // Function to find all substrings
    static List<string> findSubstrings(string s) {

        // to store all substrings
        List<string> res = new List<string>();

        // to store current string
        List<char> cur = new List<char>();
        subString(s, s.Length, 0, cur, res);
        return res;
    }

    public static void Main() {
        string s = "abc";
        List<string> res = findSubstrings(s);
        Console.WriteLine(string.Join(" ", res));
    }
}
JavaScript 
// JavaScript program to find all the
// substrings of given string

// Recursive Function to find all
// substrings of a string
function subString(s, n, index, cur, res) {

    // if we have reached the
    // end of the string
    if (index === n) {
        return;
    }

    // add the character s[index]
    // to the current string
    cur += s[index];

    // add the current string in result
    res.push(cur);

    // move to next index
    subString(s, n, index + 1, cur, res);

    // remove the current character
    // from the current string
    cur = cur.slice(0, -1);

    // if current string is empty
    // skip the current index to
    // start the new substring
    if (cur.length === 0) {
        subString(s, n, index + 1, cur, res);
    }
}

// Function to find all substrings
function findSubstrings(s) {

    // to store all substrings
    let res = [];

    // to store current string
    let cur = "";
    subString(s, s.length, 0, cur, res);
    return res;
}

const s = "abc";
const res = findSubstrings(s);
console.log(res.join(" "));

Output
a ab abc b bc c


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