## Introduction

Data Structures play a vital role in our problem-solving skills. Consistency with an efficient learning approach can raise your bar in the programming world.

This problem is about counting k length subarrays with only 1’s in the binary(0,1) string.

**What do you mean by subarray?**

It is a contiguous part of array. For example the array [1, 2, 3, 4].The subarrays are (1), (2), (3), (4), (1,2), (2,3), (3,4), (1,2,3), (2,3,4) and (1,2,3,4).

*For questions related to each data structure, refer to the blog** ** Must-Do Coding Interview Questions for Product Based Companies*.

Let’s move to our problem statement for better clarity of the problem.

## Problem Statement

We are given a binary string, and we aim to find the count of subarrays of length K that contains only 1.

Let’s understand this with some examples:

**Example1:**

Input: s= “1111110” K= 3

Output: 4

**Example2:**

Input: s= “100001” K= 1

Output: 2