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Longest Subarray having sum of elements atmost ‘k’
• Difficulty Level : Medium
• Last Updated : 23 Apr, 2021

Given an array of integers, our goal is to find the length of the largest subarray having the sum of its elements at most ‘k’ where k>0.

Examples:

```Input : arr[] = {1, 2, 1, 0, 1, 1, 0}, k = 4
Output : 5
Explanation:
{1, 2, 1} => sum = 4, length = 3
{1, 2, 1, 0}, {2, 1, 0, 1} => sum = 4, length = 4
{1, 0, 1, 1, 0} =>5 sum = 3, length = 5```

Method 1 (Brute Force)
Find all the subarrays whose sum is less than or equal to k and return the one with the largest length.
Time Complexity : O(n^2)
Method 2 (Efficient):
An efficient approach is to use the sliding window technique

1. Traverse the array and check if on adding the current element its sum is less than or equal to k.
2. If it’s less than k then add it to the sum and increase the count.
3. Keep track of Maximum count.

## C++

 `// A C++ program to find longest subarray with``// sum of elements at-least k.``#include ``using` `namespace` `std;` `// function to find the length of largest subarray``// having sum atmost k.``int` `atMostSum(``int` `arr[], ``int` `n, ``int` `k)``{``    ``int` `sum = 0;``    ``int` `cnt = 0, maxcnt = 0;` `    ``for` `(``int` `i = 0; i < n; i++) {``        ` `        ``// If adding current element doesn't``        ``// cross limit add it to current window``        ``if` `((sum + arr[i]) <= k) {``            ``sum += arr[i];``            ``cnt++;``        ``}` `        ``// Else, remove first element of current``        ``// window and add the current element``        ``else` `if``(sum!=0)``        ``{``            ``sum = sum - arr[i - cnt] + arr[i];``        ``}` `        ``// keep track of max length.``        ``maxcnt = max(cnt, maxcnt);``    ``}``    ``return` `maxcnt;``}` `// Driver function``int` `main()``{``    ``int` `arr[] = {1, 2, 1, 0, 1, 1, 0};``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);``    ``int` `k = 4;` `    ``cout << atMostSum(arr, n, k);``    ``return` `0;``}`

## Java

 `// Java program to find longest subarray with``// sum of elements at-least k.``import` `java.util.*;` `class` `GFG {``    ` `    ``// function to find the length of largest``    ``// subarray having sum atmost k.``    ``public` `static` `int` `atMostSum(``int` `arr[], ``int` `n,``                                        ``int` `k)``    ``{``        ``int` `sum = ``0``;``        ``int` `cnt = ``0``, maxcnt = ``0``;``    ` `        ``for` `(``int` `i = ``0``; i < n; i++) {``            ` `            ``// If adding current element doesn't``            ``// cross limit add it to current window``            ``if` `((sum + arr[i]) <= k) {``                ``sum += arr[i];``                ``cnt++;``            ``}``    ` `            ``// Else, remove first element of current``            ``// window.``            ``else` `if``(sum!=``0``)``           ``{``            ``sum = sum - arr[i - cnt] + arr[i];``           ``}``    ` `            ``// keep track of max length.``            ``maxcnt = Math.max(cnt, maxcnt);``        ``}``        ``return` `maxcnt;``    ``}``    ` `    ``/* Driver program to test above function */``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int` `arr[] = { ``1``, ``2``, ``1``, ``0``, ``1``, ``1``, ``0` `};``        ``int` `n = arr.length;``        ``int` `k = ``4``;``    ` `        ``System.out.print(atMostSum(arr, n, k));``            ` `    ``}``}``// This code is contributed by Arnav Kr. Mandal.`

## Python3

 `# Python3 program to find longest subarray``# with sum of elements at-least k.` `# function to find the length of largest``# subarray having sum atmost k.``def` `atMostSum(arr, n, k):``    ``_sum ``=` `0``    ``cnt ``=` `0``    ``maxcnt ``=` `0``    ` `    ``for` `i ``in` `range``(n):` `        ``# If adding current element doesn't``        ``# Cross limit add it to current window``        ``if` `((_sum ``+` `arr[i]) <``=` `k):``            ``_sum ``+``=` `arr[i]``            ``cnt ``+``=` `1``        ` `        ``# Else, remove first element of current``        ``# window and add the current element``        ``elif``(``sum` `!``=` `0``):``            ``_sum ``=` `_sum ``-` `arr[i ``-` `cnt] ``+` `arr[i]``        ` `        ``# keep track of max length.``        ``maxcnt ``=` `max``(cnt, maxcnt)` `    ``return` `maxcnt``    ` `# Driver function``arr ``=` `[``1``, ``2``, ``1``, ``0``, ``1``, ``1``, ``0``]``n ``=` `len``(arr)``k ``=` `4``print``(atMostSum(arr, n, k))` `# This code is contributed by "Abhishek Sharma 44"`

## C#

 `// C# program to find longest subarray``// with sum of elements at-least k.``using` `System;` `class` `GFG {``    ` `    ``// function to find the length of largest``    ``// subarray having sum atmost k.``    ``public` `static` `int` `atMostSum(``int` `[]arr, ``int` `n,``                                           ``int` `k)``    ``{``        ``int` `sum = 0;``        ``int` `cnt = 0, maxcnt = 0;``    ` `        ``for` `(``int` `i = 0; i < n; i++) {``            ` `            ``// If adding current element doesn't``            ``// cross limit add it to current window``            ``if` `((sum + arr[i]) <= k) {``                ``sum += arr[i];``                ``cnt++;``            ``}``    ` `            ``// Else, remove first element``            ``// of current window.``            ``else` `if``(sum!=0)``            ``{``                ``sum = sum - arr[i - cnt] + arr[i];``            ``}``    ` `            ``// keep track of max length.``            ``maxcnt = Math.Max(cnt, maxcnt);``        ``}``        ``return` `maxcnt;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `Main()``    ``{``        ``int` `[]arr = {1, 2, 1, 0, 1, 1, 0};``        ``int` `n = arr.Length;``        ``int` `k = 4;``    ` `        ``Console.Write(atMostSum(arr, n, k));``            ` `    ``}``}` `// This code is contributed by Nitin Mittal`

## PHP

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## Javascript

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Output:

`5`

Time Complexity : O(n)
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