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

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