I want to find the length smallest subarray whose sum is equal to k.

```
Input: arr[] = {2, 4, 6, 10, 2, 1}, K = 12
Output: 2
```

Explanation:

All possible subarrays with sum 12 are `{2, 4, 6}`

and `{10, 2}`

.

```
Input: arr[] = { 1, 2, 4, 3, 2, 4, 1 }, K = 7
Output: 2
```