# Reduce given array by replacing subarrays with values less than K with their sum

• Difficulty Level : Easy
• Last Updated : 23 Sep, 2021

Given an array arr[] consisting of N positive integers and a positive integer K, the task is to update the given array by replacing the subarrays that are less than K with the sum of the elements in that subarray.

Examples:

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Input: arr[] = {200, 6, 36, 612, 121, 66, 63, 39, 668, 108}, K = 100
Output: 200 42 612 121 168 668 108
Explanation:
The  subarray arr[1, 2] i.e., {6, 36} have elements less than K(= 100). So, adding and insert them into array as 6 + 36 = 42.
The  subarray arr[5, 7] i.e., {66, 63, 39} have elements less than K(= 100). So, adding and insert them into array as 66 + 63 + 39 = 168.
The modified array is {200, 42, 612, 121, 168, 668, 108}

Input: arr[] = {50, 25, 90, 21, 30}, K = 95
Output: 216

Approach: The given problem can be solved by traversing the array and keep the track of the sum having all elements less than K and update the array accordingly. Follow the steps below to solve the problem:

• Initialize the variable, say sum as 0 that stores the sum of the subarray.
• Initialize the vector, say res[] that stores the updated array arr[] satisfying the given criteria.
• Traverse the given array and if the value of arr[i] < K, then update the value of sum as the sum + arr[i]. Otherwise, update the value of sum as 0 and add the value sum and arr[i] to the vector res[].
• After completing the above steps, print the value stored in the vector res[].

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach` `#include ``using` `namespace` `std;` `// Function to replace all the subarray``// having values < K with their sum``void` `updateArray(vector<``int``>& arr, ``int` `K)``{` `    ``// Stores the sum of subarray having``    ``// elements less than K``    ``int` `sum = 0;` `    ``// Stores the updated array``    ``vector<``int``> res;` `    ``// Traverse the array``    ``for` `(``int` `i = 0; i < (``int``)arr.size(); i++) {` `        ``// Update the sum``        ``if` `(arr[i] < K) {``            ``sum += arr[i];``        ``}` `        ``// Otherwise, update the vector``        ``else` `{``            ``if` `(sum != 0) {``                ``res.push_back(sum);``            ``}``            ``sum = 0;``            ``res.push_back(arr[i]);``        ``}``    ``}` `    ``if` `(sum != 0)``        ``res.push_back(sum);` `    ``// Print the result``    ``for` `(``auto``& it : res)``        ``cout << it << ``' '``;``}` `// Driver Code``int` `main()``{` `    ``vector<``int``> arr = { 200, 6, 36, 612, 121,``                        ``66, 63, 39, 668, 108 };``    ``int` `K = 100;``    ``updateArray(arr, K);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.util.*;` `class` `GFG {` `    ``// Function to replace all the subarray``    ``// having values < K with their sum``    ``static` `void` `updateArray(``int` `[]arr, ``int` `K)``    ``{` `        ``// Stores the sum of subarray having``        ``// elements less than K``        ``int` `sum = ``0``;` `        ``// Stores the updated array``         ``ArrayList res``            ``= ``new` `ArrayList();` `        ``// Traverse the array``        ``for` `(``int` `i = ``0``; i < arr.length; i++) {` `            ``// Update the sum``            ``if` `(arr[i] < K) {``                ``sum += arr[i];``            ``}` `            ``// Otherwise, update the vector``            ``else` `{``                ``if` `(sum != ``0``) {``                    ``res.add(sum);``                ``}``                ``sum = ``0``;``                ``res.add(arr[i]);``            ``}``        ``}` `        ``if` `(sum != ``0``)``            ``res.add(sum);` `        ``// Print the result``        ``for` `(``int` `i = ``0``; i < res.size(); i++)``            ``System.out.print(res.get(i) + ``" "``);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String []args)``    ``{` `        ``int` `[]arr = {``200``, ``6``,  ``36``, ``612``, ``121``,``                             ``66``,  ``63``, ``39``, ``668``, ``108` `};``        ``int` `K = ``100``;``        ``updateArray(arr, K);``    ``}``}` `// This code is contributed by SURENDRA_GANGWAR.`

## Python3

 `# python program for the above approach` `# Function to replace all the subarray``# having values < K with their sum``def` `updateArray(arr, K):` `    ``# Stores the sum of subarray having``    ``# elements less than K``    ``sum` `=` `0` `    ``# Stores the updated array``    ``res ``=` `[]` `    ``# Traverse the array``    ``for` `i ``in` `range``(``0``, ``int``(``len``(arr))):` `        ``# Update the sum``        ``if` `(arr[i] < K):``            ``sum` `+``=` `arr[i]` `        ``# Otherwise, update the vector``        ``else``:``            ``if` `(``sum` `!``=` `0``):``                ``res.append(``sum``)` `            ``sum` `=` `0``            ``res.append(arr[i])` `    ``if` `(``sum` `!``=` `0``):``        ``res.append(``sum``)` `    ``# Print the result``    ``for` `it ``in` `res:``        ``print``(it, end``=``" "``)`  `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``arr ``=` `[``200``, ``6``, ``36``, ``612``, ``121``, ``66``, ``63``, ``39``, ``668``, ``108``]``    ``K ``=` `100``    ``updateArray(arr, K)``    ` `# This code is contributed by rakeshsahni`

## C#

 `// C# program for the above approach` `using` `System;``using` `System.Collections.Generic;``class` `GFG {` `    ``// Function to replace all the subarray``    ``// having values < K with their sum``    ``static` `void` `updateArray(List<``int``> arr, ``int` `K)``    ``{` `        ``// Stores the sum of subarray having``        ``// elements less than K``        ``int` `sum = 0;` `        ``// Stores the updated array``        ``List<``int``> res = ``new` `List<``int``>();` `        ``// Traverse the array``        ``for` `(``int` `i = 0; i < arr.Count; i++) {` `            ``// Update the sum``            ``if` `(arr[i] < K) {``                ``sum += arr[i];``            ``}` `            ``// Otherwise, update the vector``            ``else` `{``                ``if` `(sum != 0) {``                    ``res.Add(sum);``                ``}``                ``sum = 0;``                ``res.Add(arr[i]);``            ``}``        ``}` `        ``if` `(sum != 0)``            ``res.Add(sum);` `        ``// Print the result``        ``foreach``(``int` `it ``in` `res) Console.Write(it + ``" "``);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main()``    ``{` `        ``List<``int``> arr``            ``= ``new` `List<``int``>{ 200, 6,  36, 612, 121,``                             ``66,  63, 39, 668, 108 };``        ``int` `K = 100;``        ``updateArray(arr, K);``    ``}``}` `// This code is contributed by ukasp.`

## Javascript

 ``
Output:
`200 42 612 121 168 668 108`

Time Complexity: O(N)
Auxiliary Space: O(1)

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