> For the complete documentation index, see [llms.txt](https://gl01.gitbook.io/gfg-editorials/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl01.gitbook.io/gfg-editorials/2023/12-2023-dec-10/11-max-sum-subarray-of-size-k.md).

# 11. Max Sum Subarray of size K

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/max-sum-subarray-of-size-k5313/1)

![](https://badgen.net/badge/Level/Easy/green)

## My Approach

Easy approach, I use a sliding window approach. I maintain a running sum of the current window and slide the window by subtracting the element that goes out of the window and adding the new element. I update the maximum sum at each step.

## Time and Auxiliary Space Complexity

* **Time Complexity**: O(N), where N is the size of the array.
* **Auxiliary Space Complexity**: O(1).

## Code (C++)

```cpp
class Solution {   
public:
    long maximumSumSubarray(int K, vector<int> &Arr , int N){
        long out = 0;
        long sum = 0;
        for(int i = 0; i < N ; ++i){
            sum += Arr[i];
            if(i >= K)
                sum -= Arr[i - K];
            
            out = max(out, sum);
        }
        return out;
    }
};
```

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