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In an array `nums` containing only 0s and 1s, a `k`-bit flip consists of choosing a (contiguous) subarray of length `k` 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`.

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 can't 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]
```

Note:

1. `1 <= nums.length <= 30000`
2. `1 <= k <= nums.length`

class Solution { public int minKBitFlips(int[] nums, int k) { } }
Medium