public class Solution
extends Object
995 - Minimum Number of K Consecutive Bit Flips\.
Hard
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 <= 105
* `1 <= k <= nums.length`