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Find all subsequences with sum equals to K
• Difficulty Level : Hard
• Last Updated : 08 Dec, 2020

Given an array arr[] of length N and a number K, the task is to find all the subsequences of the array whose sum of elements is K

Examples:

Input: arr[] = {1, 2, 3}, K = 3
Output:
1 2
3

Input: arr[] = {17, 18, 6, 11, 2, 4}, K = 6
Output:
2 4
6 Approach:
The idea is to use the jagged array to store the subsequences of the array of different lengths.For every element in the array, there are mainly two choices for it that is either to include in the subsequence or not. Apply this for every element in the array by reducing the sum, if the element is included otherwise search for the subsequence without including it.

Below is the implementation of the above approach:

## C++

 `// C++ implemenation to find all the``// subsequence whose sum is K` `#include ``using` `namespace` `std;` `// Utility function to find the subsequences``// whose sum of the element is K``int` `subsetSumToK(``int` `arr[], ``int` `n,``            ``int` `output[], ``int` `k){``    ` `    ``// Base Case``    ``if` `(n == 0) {``        ``if` `(k == 0) {``            ``output = 0;``            ``return` `1;``        ``}``        ``else` `{``            ``return` `0;``        ``}``    ``}``    ` `    ``// Array to store the subsequences``    ``// which includes the element arr``    ``int` `output1;``    ` `    ``// Array to store the subsequences``    ``// which not includes the element arr``    ``int` `output2;``    ` `    ``// Recursive call to find the subsequences``    ``// which includes the element arr``    ``int` `size1 = subsetSumToK(arr + 1,``        ``n - 1, output1, k - arr);``    ` `    ``// Recursive call to find the subsequences``    ``// which not includes the element arr``    ``int` `size2 = subsetSumToK(arr + 1, n - 1,``                                ``output2, k);` `    ``int` `i, j;``    ` `    ``// Loop to update the results of the``    ``// Recursive call of the function``    ``for` `(i = 0; i < size1; i++) {``        ` `        ``// Incremeing the length of``        ``// jagged array because it includes``        ``// the arr element of the array``        ``output[i] = output1[i] + 1;``        ` `        ``// In the first column of the jagged``        ``// array put the arr element``        ``output[i] = arr;``    ``}``    ` `    ``// Loop to update the subsequence``    ``// in the output array``    ``for` `(i = 0; i < size1; i++) {``        ``for` `(j = 1; j <= output1[i]; j++) {``            ``output[i][j + 1] = output1[i][j];``        ``}``    ``}``    ` `    ``// Loop to update the subsequnces``    ``// which do not include the arr element``    ``for` `(i = 0; i < size2; i++) {``        ``for` `(j = 0; j <= output2[i]; j++) {``            ``output[i + size1][j] = output2[i][j];``        ``}``    ``}``    ` `    ``return` `size1 + size2;``}` `// Function to find the subsequences``// whose sum of the element is K``void` `countSubsequences(``int` `arr[], ``int` `n,``            ``int` `output[], ``int` `k)``{  ``    ``int` `size = subsetSumToK(arr, n, output, k);``    ` `    ``for` `(``int` `i = 0; i < size; i++) {``        ``for` `(``int` `j = 1; j <= output[i]; j++) {``            ``cout << output[i][j] << ``" "``;``        ``}``        ``cout << endl;``    ``}   ``}` `// Driver Code``int` `main()``{``    ``int` `arr[] = {5, 12, 3, 17, 1, 18, 15, 3, 17};``    ``int` `length = 9, output, k = 6;` `    ``countSubsequences(arr, length, output, k);` `    ``return` `0;``}`

## Java

 `// Java implementation to find all the``// sub-sequences whose sum is K` `import` `java.util.*;``public` `class` `SubsequenceSumK {` `    ``// Function to find the subsequences``    ``// with given sum``    ``public` `static` `void` `subSequenceSum(``        ``ArrayList> ans,``        ``int` `a[], ArrayList temp,``                        ``int` `k, ``int` `start)``    ``{``        ``// Here we have used ArrayList``        ``// of ArrayList in in Java for``        ``// implementation of Jagged Array` `        ``// if k < 0 then the sum of``        ``// the current subsequence``        ``// in temp is greater than K``        ``if``(start > a.length || k < ``0``)``            ``return` `;` `        ``// if(k==0) means that the sum``        ``// of this subsequence``        ``// is equal to K``        ``if``(k == ``0``)``        ``{``            ``ans.add(``             ``new` `ArrayList(temp)``             ``);``            ``return` `;``        ``}``        ``else` `{``            ``for` `(``int` `i = start;``                 ``i < a.length; i++) {` `                ``// Adding a new``                ``// element into temp``                ``temp.add(a[i]);` `                ``// After selecting an``                ``// element from the``                ``// array we subtract K``                ``// by that value``                ``subSequenceSum(ans, a,``                   ``temp, k - a[i],i+``1``);` `                ``// Remove the lastly``                ``// added element``                ``temp.remove(temp.size() - ``1``);``            ``}``        ``}``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `arr[] = {``5``, ``12``, ``3``, ``17``, ``1``,``                     ``18``, ``15``, ``3``, ``17``};``        ``int` `k = ``6``;``        ``ArrayList> ans;``        ``ans= ``new` `ArrayList<``                  ``ArrayList>();``        ``subSequenceSum(ans, arr,``            ``new` `ArrayList(), k, ``0``);``            ` `        ``// Loop to print the subsequences``        ``for``(``int` `i = ``0``; i < ans.size();``         ``i++){``            ``for``(``int` `j = ``0``;``              ``j < ans.get(i).size(); j++){``                ``System.out.print(``                    ``ans.get(i).get(j));``                ``System.out.print(``" "``);``            ``}``            ``System.out.println();``        ``}``    ``}``}`

## Python3

 `# Python3 implemenation to find all the``# subsequence whose sum is K`` ` `# Utility function to find the subsequences``# whose sum of the element is K``def` `subsetSumToK(arr, n, output, k):``     ` `    ``# Base Case``    ``if` `(n ``=``=` `0``):``        ``if` `(k ``=``=` `0``):``            ``output[``0``][``0``] ``=` `0``;``            ``return` `1``;``        ``else``:``            ``return` `0``;``     ` `    ``# Array to store the subsequences``    ``# which includes the element arr   ``    ``output1 ``=` `[[``0` `for` `j ``in` `range``(``50``)] ``for` `i ``in` `range``(``1000``)]``     ` `    ``# Array to store the subsequences``    ``# which not includes the element arr``    ``output2 ``=` `[[``0` `for` `j ``in` `range``(``50``)] ``for` `i ``in` `range``(``1000``)]``     ` `    ``# Recursive call to find the subsequences``    ``# which includes the element arr``    ``size1 ``=` `subsetSumToK(arr[``1``:], n ``-` `1``, output1, k ``-` `arr[``0``]);``     ` `    ``# Recursive call to find the subsequences``    ``# which not includes the element arr``    ``size2 ``=` `subsetSumToK(arr[``1``:], n ``-` `1``, output2, k)``     ` `    ``# Loop to update the results of the``    ``# Recursive call of the function``    ``for` `i ``in` `range``(size1):``         ` `        ``# Incremeing the length of``        ``# jagged array because it includes``        ``# the arr element of the array``        ``output[i][``0``] ``=` `output1[i][``0``] ``+` `1``;``         ` `        ``# In the first column of the jagged``        ``# array put the arr element``        ``output[i][``1``] ``=` `arr[``0``];``     ` `    ``# Loop to update the subsequence``    ``# in the output array``    ``for` `i ``in` `range``(size1):``        ``for` `j ``in` `range``(``1``, output1[i][``0``]``+``1``):  ``            ``output[i][j ``+` `1``] ``=` `output1[i][j];``     ` `    ``# Loop to update the subsequnces``    ``# which do not include the arr element``    ``for` `i ``in` `range``(size2):``        ``for` `j ``in` `range``(output2[i][``0``] ``+` `1``):``            ``output[i ``+` `size1][j] ``=` `output2[i][j];``     ` `    ``return` `size1 ``+` `size2;` `# Function to find the subsequences``# whose sum of the element is K``def` `countSubsequences(arr, n, output, k):``    ``size ``=` `subsetSumToK(arr, n, output, k);``    ``for` `i ``in` `range``(size):    ``        ``for` `j ``in` `range``(``1``, output[i][``0``] ``+` `1``):``            ``print``(output[i][j], end ``=` `' '``)``        ``print``()``        ` `# Driver Code``if` `__name__``=``=``'__main__'``:` `    ``arr ``=` `[``5``, ``12``, ``3``, ``17``, ``1``, ``18``, ``15``, ``3``, ``17``]``    ``length ``=` `9``    ``output ``=` `[[``0` `for` `j ``in` `range``(``50``)] ``for` `i ``in` `range``(``1000``)]``    ``k ``=` `6``;`` ` `    ``countSubsequences(arr, length, output, k);` `  ``# This code is contributed by rutvik_56.`

## C#

 `// C# implemenation to find all the``// subsequence whose sum is K``using` `System;``using` `System.Collections;``using` `System.Collections.Generic;` `class` `GFG{``    ` `// Function to find the subsequences``// with given sum``public` `static` `void` `subSequenceSum(``    ``List> ans, ``int``[] a,``    ``List<``int``> temp, ``int` `k, ``int` `start)``{``    ` `    ``// Here we have used ArrayList``    ``// of ArrayList in in Java for ``    ``// implementation of Jagged Array` `    ``// If k < 0 then the sum of``    ``// the current subsequence``    ``// in temp is greater than K``    ``if` `(start > a.Length || k < 0)``        ``return``;` `    ``// If (k==0) means that the sum ``    ``// of this subsequence``    ``// is equal to K``    ``if` `(k == 0)``    ``{``        ``ans.Add(``new` `List<``int``>(temp));``        ``return``;``    ``}``    ``else``    ``{``        ``for``(``int` `i = start;``                ``i < a.Length; i++)``        ``{``            ` `            ``// Adding a new ``            ``// element into temp``            ``temp.Add(a[i]);` `            ``// After selecting an``            ``// element from the``            ``// array we subtract K``            ``// by that value``            ``subSequenceSum(ans, a, ``               ``temp, k - a[i], i + 1);` `            ``// Remove the lastly ``            ``// added element``            ``temp.RemoveAt(temp.Count - 1);``        ``}``    ``}``}` `// Driver code``static` `public` `void` `Main ()``{``    ``int``[] arr = { 5, 12, 3, 17, 1,``                  ``18, 15, 3, 17 };``    ``int` `k = 6;``    ` `    ``List> ans = ``new` `List>();``    ` `    ``subSequenceSum(ans, arr,``    ``new` `List<``int``>(), k, 0);``    ` `    ``// Loop to print the subsequences``    ``for``(``int` `i = 0; i < ans.Count; i++)``    ``{``        ``for``(``int` `j = 0; j < ans[i].Count; j++)``        ``{``            ``Console.Write(ans[i][j] + ``" "``);``        ``}``        ``Console.WriteLine();``    ``} ``}``}` `// This code is contributed by offbeat`
Output:
```5 1
3 3```

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