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# 0995. Minimum Number of K Consecutive Bit Flips

<https://leetcode.com/problems/minimum-number-of-k-consecutive-bit-flips>

## Description

You are given a binary array `nums` and an integer `k`.

A **k-bit flip** is choosing a **subarray** of length `k` from `nums` and simultaneously changing every `0` in the subarray to `1`, and every `1` in the subarray to `0`.

Return *the minimum number of **k-bit flips** required so that there is no* `0` *in the array*. If it is not possible, return `-1`.

A **subarray** is a **contiguous** part of an array.

**Example 1:**

```
**Input:** nums = [0,1,0], k = 1
**Output:** 2
**Explanation:** Flip nums[0], then flip nums[2].
```

**Example 2:**

```
**Input:** nums = [1,1,0], k = 2
**Output:** -1
**Explanation:** No matter how we flip subarrays of size 2, we cannot make the array become [1,1,1].
```

**Example 3:**

```
**Input:** nums = [0,0,0,1,0,1,1,0], k = 3
**Output:** 3
**Explanation:** 
Flip nums[0],nums[1],nums[2]: nums becomes [1,1,1,1,0,1,1,0]
Flip nums[4],nums[5],nums[6]: nums becomes [1,1,1,1,1,0,0,0]
Flip nums[5],nums[6],nums[7]: nums becomes [1,1,1,1,1,1,1,1]
```

**Constraints:**

* `1 <= nums.length <= 3 * 104`
* `1 <= k <= nums.length`

## ac

```java
```