Generating All Subarrays (original) (raw)

Last Updated : 07 Feb, 2025

Try it on GfG Practice

Given an array arr[], the task is to generate all the possible subarrays of the given array.

**Examples:

**Input: arr[] = [1, 2, 3]
**Output: [ [1], [1, 2], [2], [1, 2, 3], [2, 3], [3] ]

**Input: arr[] = [1, 2]
**Output: [ [1], [1, 2], [2] ]

**Iterative Approach

To generate a subarray, we need a **starting index from the original array. For choosing the starting index, we can run a loop from **[0 to n-1] and consider each i as the starting index. For each starting index **i, we can select an ending index from the range **[i to n-1]. A nested loop from **[i to n-1] will help in selecting the **ending index. Once we have the starting and ending indices, we need an innermost loop to print the elements in this subarray.

• Outermost Loop: Picks starting index of current subarray
• Middle Loop: Picks ending index of current subarray
• Innermost Loop: Prints the subarray from the starting index to the ending index C++ `

#include #include using namespace std;

// Prints all subarrays in arr[0..n-1] void subArray(vector &arr) { int n = arr.size();

// Pick starting point
for (int i = 0; i < n; i++)
{
    // Pick ending poin
    for (int j = i; j < n; j++)
    {
        // Print subarray between current starting
        // and ending points
        for (int k = i; k <= j; k++)
            cout << arr[k] << " ";
        cout << endl;
    }
}

}

int main() { vector arr = {1, 2, 3, 4}; cout << "All Non-empty Subarrays\n"; subArray(arr); return 0; }

C

#include <stdio.h>

//Prints all subarrays in arr[0..n-1] void subArray(int arr[], int n) {

// Pick starting point
for (int i = 0; i < n; i++) {
  
    // Pick ending point
    for (int j = i; j < n; j++) {
      
        // Print subarray between current starting and ending points
        for (int k = i; k <= j; k++) {
            printf("%d ", arr[k]);
        }
        printf("\n");
    }
}

}

int main() { int arr[] = {1, 2, 3, 4}; int n = sizeof(arr) / sizeof(arr[0]); printf("All Non-empty Subarrays:\n"); subArray(arr, n); return 0; }

Java

import java.util.ArrayList;

public class GfG {

  //Prints all subarrays in arr[0..n-1]
static void subArray(ArrayList<Integer> arr) {
    int n = arr.size();

    // Pick starting point
    for (int i = 0; i < n; i++) {
      
        // Pick ending point
        for (int j = i; j < n; j++) {
          
            // Print subarray between current starting and ending points
            for (int k = i; k <= j; k++) {
                System.out.print(arr.get(k) + " ");
            }
            System.out.println();
        }
    }
}

public static void main(String[] args) {
    ArrayList<Integer> arr = new ArrayList<>();
    arr.add(1);
    arr.add(2);
    arr.add(3);
    arr.add(4);
    System.out.println("All Non-empty Subarrays:");
    subArray(arr);
}

}

Python

#Prints all subarrays in arr[0..n-1] def sub_array(arr): n = len(arr)

# Pick starting point
for i in range(n):
    # Pick ending point
    for j in range(i, n):
        # Print subarray between current starting and ending points
        for k in range(i, j + 1):
            print(arr[k], end=" ")
        print()  # New line after each subarray

Driver code

arr = [1, 2, 3, 4] print("All Non-empty Subarrays:") sub_array(arr)

C#

using System; using System.Collections.Generic;

class GfG {

  //Prints all subarrays in arr[0..n-1]
static void SubArray(List<int> arr) {
    int n = arr.Count;

    // Pick starting point
    for (int i = 0; i < n; i++) {
      
        // Pick ending point
        for (int j = i; j < n; j++) {
          
            // Print subarray between current starting and ending points
            for (int k = i; k <= j; k++) {
                Console.Write(arr[k] + " ");
            }
            Console.WriteLine();
        }
    }
}

static void Main() {
    List<int> arr = new List<int> { 1, 2, 3, 4 };
    Console.WriteLine("All Non-empty Subarrays:");
    SubArray(arr);
}

}

JavaScript

//Prints all subarrays in arr[0..n-1] function subArray(arr) { const n = arr.length;

// Pick starting point
for (let i = 0; i < n; i++) {

    // Pick ending point
    for (let j = i; j < n; j++) {
    
        // Print subarray between current starting and ending points
        let subarr = [];
        for (let k = i; k <= j; k++) {
            subarr.push(arr[k]);
        }
        console.log(subarr.join(" "));
    }
}

}

const arr = [1, 2, 3, 4]; console.log("All Non-empty Subarrays:"); subArray(arr);

`

Output

All Non-empty Subarrays 1 1 2 1 2 3 1 2 3 4 2 2 3 2 3 4 3 3 4 4

**Recursive Approach

We use two pointers **start and **end to maintain the starting and ending point of the array and follow the steps given below:

• Stop if we have reached the end of the array
• Increment the **end index if **start has become greater than **end
• Print the subarray from index **start to **end and increment the starting index

Below is the implementation of the above approach.

C++ `

// C++ code to print all possible subarrays for given array // using recursion #include #include using namespace std;

// Recursive function to print all possible subarrays for given array void printSubArrays(vector& arr, int start, int end) {

// Stop if we have reached the end of the array
if (end == arr.size())
    return;

// Increment the end point and reset the start to 0
else if (start > end)
    printSubArrays(arr, 0, end + 1);

// Print the subarray and increment the starting point
else {
    for (int i = start; i <= end; i++)  
        cout << arr[i] << " ";
    cout << endl;
    printSubArrays(arr, start + 1, end);  
}

}

int main() { vector arr = {1, 2, 3}; printSubArrays(arr, 0, 0); return 0; }

C

// C code to print all possible subarrays for given array // using recursion #include <stdio.h>

// Recursive function to print all possible subarrays for // given array void printSubArrays(int arr[], int start, int end, int size) {

// Stop if we have reached the end of the array
if (end == size)
    return;

// Increment the end point and start from 0
else if (start > end)
    printSubArrays(arr, 0, end + 1, size);

// Print the subarray and increment the starting point
else {
    printf("[");
    for (int i = start; i < end; i++)
        printf("%d, ", arr[i]);
        printf("%d]\n", arr[end]);
        printSubArrays(arr, start + 1, end, size);
}
return;

}

int main() { int arr[] = { 1, 2, 3 }; int n = sizeof(arr) / sizeof(arr[0]); printSubArrays(arr, 0, 0, n); return 0; }

Java

// Java code to print all possible subarrays for given array // using recursion

class solution {

// Recursive function to print all possible subarrays
// for given array
static void printSubArrays(int[] arr, int start, int end)
{ 
    // Stop if we have reached the end of the array
    if (end == arr.length)
        return;
    // Increment the end point and start from 0
    else if (start > end)
        printSubArrays(arr, 0, end + 1);
    // Print the subarray and increment the starting
    // point
    else {
        System.out.print("[");
        for (int i = start; i < end; i++)
            System.out.print(arr[i] + ", ");
        System.out.println(arr[end] + "]");
        printSubArrays(arr, start + 1, end);
    }
    return;
}

public static void main(String args[])
{
    int[] arr = { 1, 2, 3 };
    printSubArrays(arr, 0, 0);
}

}

Python

Python3 code to print all possible subarrays

for given array using recursion

Recursive function to print all possible subarrays

for given array

def printSubArrays(arr, start, end):

# Stop if we have reached the end of the array    
if end == len(arr):
    return

# Increment the end point and start from 0
elif start > end:
    return printSubArrays(arr, 0, end + 1)
    
# Print the subarray and increment the starting
# point
else:
    print(arr[start:end + 1])
    return printSubArrays(arr, start + 1, end)
    

Driver code

arr = [1, 2, 3] printSubArrays(arr, 0, 0)

C#

// C# code to print all possible subarrays // for given array using recursion using System;

class GFG {

// Recursive function to print all  
// possible subarrays for given array 
static void printSubArrays(int []arr, 
                    int start, int end) 
{ 
    // Stop if we have reached 
    // the end of the array 
    if (end == arr.Length) 
        return; 

    // Increment the end point 
    // and start from 0 
    else if (start > end) 
        printSubArrays(arr, 0, end + 1); 

    // Print the subarray and 
    // increment the starting point 
    else
    { 
        Console.Write("["); 
        for (int i = start; i < end; i++)
        { 
            Console.Write(arr[i]+", "); 
        } 

        Console.WriteLine(arr[end]+"]"); 
        printSubArrays(arr, start + 1, end); 
    } 
    return; 
} 

// Driver code
public static void Main(String []args) 
{ 
    int []arr = {1, 2, 3}; 
    printSubArrays(arr, 0, 0); 
} 

}

JavaScript

// JavaScript code to print all possible // subarrays for given array using recursion

// Recursive function to print all // possible subarrays for given array function printSubArrays(arr, start, end) {
if (end == arr.length) return;

// Increment the end point and start
// from 0 
else if (start > end) 
    printSubArrays(arr, 0, end + 1);
      
// Print the subarray and increment 
// the starting point 
else {
    let subArray = "[";
    for (var i = start; i < end; i++) {
        subArray += arr[i] + ", ";
    }
    subArray += arr[end] + "]";
    console.log(subArray);
    printSubArrays(arr, start + 1, end);
}
return;

}

var arr = [1, 2, 3]; printSubArrays(arr, 0, 0);

`

Output

1 1 2 2 1 2 3 2 3 3

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